Needsomeonetotalkto, I really do see where you are coming from and agree with lots of your points.
Dh and I have no family living nearby and when we moved to this area a few years ago, lost all our local social network.
As I got to know local parents, I found many friendships started and stopped at playdates. Most of the mothers had lived in the area for ages, had extended family and lots of friends already, so their evenings and weekends were pretty booked up.
Realising this, I tried not to take it personally, but it still made me feel a bit second best at times
But what I found really insensitive were the mothers (just one or two) who used to tell meet for a playdate then sit there telling me about a brilliant night out they'd had with their friends
One mother in particular made it crystal clear she had categorised me as a playdate friend. We saw a lot of each other - most weeks our sons would meet up. We often used to chat over a glass or two of wine at my house or hers. She was a single mother, but had family nearby to babysit so could go out a lot. I vaguely knew many of the people she socialised with - a nice crowd of people. She kept half inviting me to things, as she knew I was keen to see her for child-free socialising but, when we talked about it made it clear that actually she saw me as her friend for playdates or when she wanted a quiet night in drinking wine with someone...where she would regale me about her evenings out with her friends....
Considering how much time we spent together over the two years I knew her, I found it quite insulting to be categorised like this and distanced myself from her.