I've had and have several guitars and have played 7s for years. For my latest band, I'm actually going back to 6 string to get a more tighter, focused sound. Guitars are a tool - use the right tool for the job. If you'll never want a job that'll utilize the 7 string, you'll probably be happier with a 6.
I'd say firstly reflect on your mindset:
If you only play guitar to cover songs you like and you don't like any bands that use extended ranges, then there's no need for you to get it. I think this is a perfectly reasonable stance, but you have to be honest about it if that's what it is. It's not "wrong" at all, just what it is. Being on an extended guitar forum though, you may not get a lot of balanced responses on this.
If you play guitar but don't necessarily care to play what other people do, then an extended range guitar is great as it increases your musical possibilities. Sometimes it just takes time to get to this point, or sometimes you never get here (and, again, neither is a "better" for you). Forcing yourself to play 7 because people tell you its "better" is not a good idea though since you'll probably never be very happy or comfortable with that . Let it happen naturally.
Lastly, when people say things like "convince me to get... " they pretty much already know the answer anyways
Do what you need to do!