Cheap, pocket sized, and has 2 SIM card slots. Looks like a winner to me.

When you arrive at an incall with a dead battery.  I think texting is going to be a problem as well.

I've traveled abroad and gone mongering here for the past few years with an iPhone 6 and an iPhone 7.  And before that with a Galaxy S3.  Nice size, loads of functionality and no need for a new chip when out of the country.  Why would I want that dinky little thing?

One is the cost, no matter how good an international plan you have, making local calls from your US phone is VERY expensive compared to using a local carrier. Another is getting incoming calls from locals, without a new chip from whatever country you are in callers are forced to call your US number which can be confusing to the locals. Having two chips in your phone also allows you to have both a local and a US number on just one device.

I would love to get back to the days of being able to dial and answer a phone with just one hand.

It costs no more than $10 a day and even that charge is not imposed if you don't make (or receive) a call from the US on any given day.  If you make a lot of calls to the US that can get expensive, but I don't.  I think it cost me about $30 for the 6 weeks I was in Panama and CR last winter.
Your point about calls from the locals is interesting but I don't use my phone to contact them.  I walk down to the Cocal and talk to them.

As you know, the CoCal is dead during the daytime so for those of us who want to get laid both in the daytime and the nighttime it's very helpful to have a local phone and phone number.

If in major cities like Berlin T-mobile might work fine. Go to the south of Germany and you may not have good reception or no reception. It pays to get a local sim card from a phone shop.

Check out the hushed app! it lets you change your number. No need for an additional phone.

I wonder why I see people use burner phones and etc....when there are plenty of cheap or FREE apps to download to get a second or third line? Google Voice for example

You have to remember the demographic. Most mongers didn't have a computer until their 20's, and didn't have a smartphone until recently. Not the most tech-savvy bunch.

One perk of my current job is that they pay my monthly cell phone bill, and they upgraded me to a brand new iPhone. Unfortunately, I am not supposed to put music, apps, etc on the phone unless I can show a work-related need. So I would need to get a burner phone instead of using a burner app, if necessary. Fortunately, my gf trusts me and doesn't go snooping on my phone.

It's not just the demographic. Many married guys keep their monger phones, computers etc separate from their personal equipment. Even though my wife is barely computer literate I don't want a hobby burner number on my main phone.