While most guys may like big boobs, I couldn't care less about her cup size because I'm into legs.
To each his own.

Happens In Porn All the Time Too

Mostly because of the age old idea that bigger is better

You see those are old pictures when they were still 34C and in shape. Now they've gained some wait and are now 36D's. Pretty simple, kinda of like when they say they are 30-32 and really they are 36-40.

They probably dont want to see me

I only see ladies with C and under!

Personally, I would love a full C cup and a smaller back lol. Aint happening any time soon.  

Most men keep it real. I laugh when I see they lie about measurements....  
I'm only 5'3 130 34c/ 28/ 35  
And see females that are bigger than me and they lie and put a size 4 or a smaller waist of 24. Now that's alot of fs!  
Then they get mad when a review mentions " they are bigger" than the pics.  

Well, life goes on.

Because just like the U.S. Government

Hookers are not subject to "Truth in Advertising" laws.

tits

just bring your tape measure to every session..i am sure they would adore you..you can also use it to measure your dick after her tits..i love fun times..

the same reason 40% of the reviews you read the guy's always mentioning or hinting about how big his dick is

I'm rocking some brand new 36DD's, and that's no lie!  The joys of plastic surgery ... no need to have to exaggerate!

36Ds A hobbyist's comment.

Sometimes it is not just the actual measurement, but the bra size.  When I'm with a woman and have the opportunity to peak, I note the bra size.  If she really  fills out a size 34 DD then its a confirmation. Some women may wear a smaller bra that they should.  

Women: have bra sizes changed over the years?  At one time a 34 C seemed very large, now the same girl will be seen in a 34D or DD.

Based solely on your statement I take it that you are deciding they are not being honest by comparing what they say to what you see in their pictures rather than seeing them in person.

Considering how often guys will say something in a review about a providers looks based on their photos and have it completely wrong I'm going to ask how you know by the picture they are not 36D's?

Unless you have measured or done as someone else stated and seen the label on the bra how can you know for sure they are being dishonest. (...and as already mentioned some could be wearing the wrong size.)

I read a review where the guy said she was definitely a B cup not a C as represented in her photos. Funny thing about that, both her TER profile and her web site clearly said she was  B cup. Push up bra? Maybe. Some of her photos were topless though.

There is no doubt many providers will "stretch the truth" and you may be correct that the ones you have in mind as you ask the question have indeed not been honest. But I'm not convinced you can determine that solely by looking at the photo.

As for why would a provider "stretch the truth" many of the other posters have given some of the most obvious reasons so I'll leave it at that.