It's a real "it depends."

SOme "no drop" rides really, really are.

Others say they are, they'll ***swear*** they are ... but they have simply forgotten or just can't believe that someone can really, honestly, go 11 mph without falling over. Once a ride leader on our "monthly all-member ride" refused to tell me the turning point of their route - I asked him *three* times - because no, really, they weren't going to drop anybody... yea, except us. The other folks turned around and went back... I caught up and had a few words, though I am not sure they were comprehended. (Something about "I think they thought you meant "together" like it says in the dictionary.")
On the other hand, other people rode with me for probably a hundred rides and I didn't even realize they were going slower because of me. My first ride, I was never in the back; they took turns rotating around (I had no idea of drafting or anything) so that I was behind somebody to block the wind, but still not "last." It wasn't until I got a lot faster that I realized they were just as happy going 16 as 12... but perhaps that's the difference, the people who need to go 19 or 20 have trouble finding happiness below that point. If you don't by the equipment to go that fast, you can push along and get the exercise and stay social (or carry your blender and ice and produce with you :-))
But unfortunately you can't tell by *asking.* Otherwise sincere and honest people will say "oh, we don't go that fast..." I think they believe it...