First, I think one needs to differentiate between AMP and no agencies and more or less independent girls in an apartment/condo and branded agencies. The AMPs are store front walk-in and, from the few times I've been to one are 50+ year old women. No real interest there other than maybe the massage. Generally their pics are all young women looking hot but I don't think I've ever heard someone claim they've ever seen on of the models in the ads.

 
The no-name agencies are the one's advertising on places like bedpage and independent's there seem to be mostly the same. You're not going to see the girl in the ad.

 
The quality of the service is generally much lower, you generally have to pay up for anything beyond the massage, but you can both control your price by choosing if you are just looking for a happy ending or want more (full body-to-body, bj or other options up to fs).

 
With the branded agencies that operate out of condos you have a better chance of seeing the girl in the ad but still will have a good percentage of cases where either the pic is someone else (may or may not be similar to the girl you'll see) or is photoshopped to make her look younger and thinner. You're also generally going to get a flat rate for everything -- though with the newish trend to BB you'll see some option pricing (BBFS, MSOG, etc.). I will almost never go to an AMP or look for an escort on placed like bedpage because the quality (in both performance, looks and ambiance of the location) is just going to be lower. I do use several of the branded agencies and avoid some of them based on how well they act. I don't worry about the pictures too much, nor do I use them in making a decision to see someone.  

 
I don't think any of these conduct their advertising or business practices because they think American men are too stupid or unable to tell the difference. They do this because they can keep making money that way. That is probably due to two things: 1) this business has a lot of one-and done type so lots of incentives to just take advantage of the customer you'll never see because there is another waiting right around the corner, and 2) some keep going back for whatever their reasons might be (probably similar thinking to mine but, in the case of the AMPs more interested in costs and tolerant of looks/performance/ambiance).