People about Cosplay...
There’s a few things – one is that you you’re going to get asked for pictures, especially if you cosplay a popular character.
For conventions, make sure that you have a way of carrying essentials on you, even if your costume doesn’t have pockets. Perhaps make a simple bag to match your costume (same color as your outfit, or decorated with a suitable design, an example being a Jedi costume with the Jedi order symbol).
Wear your costume around before the convention, to make sure that you can move around in it, or that things don’t start slipping/pinching/falling apart after a little while. At home, there’s lots of time to make adjustments and fixes.
Don’t worry if you’re not as good as some of the veteran or professional cosplayers out there. Those cosplayers started somewhere too, and with practice, you too will eventually get good.
To answer your main questions, No and No. Cosplay is supposed to be about inclusiveness, fun, and showing your love for a character.
That being said, as with any group of people, there will be jerks on both sides. There will be those that make their costumes and look down on those that buy them, and vice versa. Jerks can be found at all levels of cosplay, just like regular society. And just like regular society, you have the choice to ignore the jerks and go your own way.
If you are happy with your cosplay, not competing in a 100% bought cosplay and are having fun, that really is all that matters.
People who make their cosplays receive just as many nasty comments and critiques as those that buy them by the way.
I’m going to address this question from a different viewpoint. Why is cosplay popular amongst those that do it?
There is the factor of honoring the source material/fandom that you love. There is the creative outlet. Then there is the sharing of the work with other fans and making new connections with like-minded people. Getting complimented for your work can create a sense of accomplishment, as can having a photographer ask to take your picture. A three day event like a local comic-con or Anime/SF/Fantasy Convention can be more rewarding than a two week vacation in the tropics, to some people.
This all has a spillover effect, those that aren’t doing it, see the results and fun that those that are having and want to do it themselves next time. This keeps the world of Cosplayers growing at a currently staggering amount. I’m staff on a 2,200 person Anime Convention and we are constantly amazed at the ~60% cosplay attendance.