I'm of the opinion that every house currently being built should have a gym room. If there will be 4 people living in the house (parents + 2 kids), you're saving countless money long-term for all these gym memberships, and also avoiding pouring more gas into the atmosphere.

However, there might be things we can't predict. Cars can become environment-friendly, for instance. There are social aspects to the gym, that may be beneficial. And also the gym shoulders any cost of future equipment that you may be unable to shoulder yourself. It can always update itself quicker than you can, cos it spreads the cost to its members.

However, so many years have gone by and we're still doing the same lifts Schwarzenegger was doing!

I think we'll become robots before we figure out a fundamentally new way to train! :P

But who knows.

I think mostly it's just personality. Some people prefer the social environment of the gym, and some people can't bear to smell other people's sweaty armpits! :P