It's just like any other hobby though. If you and your friends are playing a video game like Halo or Street Fighter, are you going to get mad if they developed a stronger interest in it and dedicate themselves to getting better at it?
It's different in the fact that there is a financial factor to a CCG as opposed to the typical pay for it once style of owning a video game, but wouldn't you want people you play with to get better and offer you more competition?
Throughout high school we typically only played "kitchen table Magic" and then I became "that guy" because I wanted to play at my LGS so I started playing more competitive decks. When we quit due to people graduating and what not, we eventually came back to it but after more playing, my group has shifted towards Legacy now and they're mostly all very good players now, which is great for everyone since we have a viable pool of cards to play competitive decks and playtest against one another.
It's probably a YMMV thing but with the uber casual style I think after a while it gets pretty boring. Someone would have a life gain deck or a burn deck or a mono green creature deck and that's fine and all but to me it got kind of boring after a few years of that.
But it's alright, for casual Magic we have EDH/Commander and Planechase now for the multiplayer aspect and Cube for the limited drafting. Think my group has a solid balance overall and I'm highly thankful for that. I think my viewpoint is going to be in the minority here though.