Personals was short for "classified personal ads" where people looked for RW dating as well as p4p, among many other things. Guys/gals over 55 or 60 would know about them but the younger set def not.
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And even though you may not ask about ethinicity or size, etc many, many women do. So it's more habit than anything else I would assume.  
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Lastly, re: a selfie, I know people under 50 generally dont have an issue with them as selfies have been around for 20 years or so, but many people find them yet another intrusion into their peronal lives and an invasion of their privacy. They dont want their email associated with how they look in person and I cant blame anyone for that.

I still see ads that ask for ethnicity and age. Not the other details though. My guess is those who send that level of detail are not regulars and simply don't know what's expected. It seems like what someone would post on a Craigslist personal ad or dating website/app.

I get these physical descriptions fairly often, though. I think it’s partly because some providers do ask for things like age and race, and partly because they are hoping to make themselves sound like a more appealing client.  

I don’t mind it. It just tells me that they are concerned about presenting themselves well to me, which is sweet.

Your very open-minded and generous view of humankind is not shared by everyone. I always mention my ethnicity and age because more than a few times I've gotten literally to the door of a provider only to have her tell me she doesn't see black men. Entirely the lady's choice, but I  wish I'd known that before I drove halfway across town.

WRT age, I usually mention I'm an old codger as shorthand for "I'm not looking to jackhammer you 3x in an hour".😆 Not sure whether it's interpreted that way, but no harm in mentioning.

Ditto WRT what others have said about a selfie. I'm of the generation that just doesn't want a picture of myself floating around in the ether and landing on who knows what website, blog post, etc.

I’ve seen girls who admittedly told me in private they don’t see certain races.  You come across as you get bothered by little things. Don’t sweat the small stuff. 🌹

I'm new to this life, and the few providers I've seen have asked for that info (age, race, etc) I also include my height/weight, only because I think it's sort of relevant, but maybe it isn't.  I just like to get it out there so if they aren't comfortable, then they can either say it, or ghost me, and either way I'll move on.

I don't send a selfie, and have never been asked for it.  If it were asked, I'm not sure I'd proceed.  I don't take selfies and wouldn't want to send one to anyone. I just don't want my image to be 'out there'.  It's personal preference.  And, yes, I'm old school.

Now, with all that said, I'd probably send one to the Queen, since I think it would be considered 'private'.  But, no, I ain't sending one to just anyone.  I'll  find another provider.

some don’t want to send selfies because they think the provider won’t book with them because they are “too ugly”

My thought process is that we, as clients generally know what we’re getting via your ads which include the things you mention (age,,,height,,,weight ,,,, measurements) so I, as a 72 year old 5’ 7” inch 175 pound white male am just reciprocating !!

(see what I did there??)

posting not too long ago here that was bemoaning the fact that they not like seeing men who are obese but will soldier through it if they have to.  Likewise, there have been providers who don't want to see men of certain ethnicities.   Many providers do not see men over, or under, a certain age.  It's their business, so providers who are not desperate often to see only men that they find appealing.   Otherwise, a one-hour session can feel like two or three hours when you are watching the clock waiting for it to be over with a customer who is not your type.  

 
From a customer's viewpoint, I don't want to spend time with any provider who is not anxious to see me, so if things like age are a turnoff, I would rather have the opportunity to pass and try someone else, so I am one who does give a physical description of myself when booking.  Full disclosure with no surprises always results in a better session for everyone.  This is why I always take exception with provider photos that are shopped to the point it looks like someone else other than who answered the door when I arrived.  I try to extend them the same courtesy with how I look so they know what to expect.  It hasn't happened to me, but I have some friends here who have not told a provider what to expect and had poor sessions because the provider was put off by their physical appearance.  No one wants to have a bad session because of a failure to communicate on what to expect, so it cuts both ways.  Too much information is better than not enough, IMO.

I think they do it in hopes that you won't screen them because they told you what they look like.

A selfie may show only the face.  Anyway you don't need to focus on it if it's not of interest.