I'd love to see humans achieve interplanetary colonization in my lifespan, but that one is a lame reason: as much as we hurt Earth, it will remain much more habitable than Mars.
(We could develop the technology without going to Mars, but it might be harder to fund tech for "what if Earth's atmosphere becomes unbreathable" to completion long before that's an issue.)
If we stopped using all fossil fuels TODAY (as well as eliminated the cattle and hog industries), as in every single person on the planet, it would a few thousand years to return to pre-industrial revolution levels of CO2. We're realistically looking at a MINIMUM of 6ft increase in sea level before the end of the century (bye-bye most coastal cities unless you ring every last inch of coast with dikes). We are rapidly depleting aquifers the world around (much faster than they can replenish), we're rapidly depleting soil (creating appreciable amounts of topsoil takes centuries), population is still climbing, electricity demand the world around is climbing, someone is producing a banned ozone depleting compound ( https://arstechnica.com/science/2018/05/it-seems-someone-is-... ) etc.
It's not a lame reason, it is an extremely valid one. We need to develop the technology and means to have self-sustaining colonies (even if enclosed in habitats) off of Earth before stuff gets so bad here we simply don't have the resources to commit to doing such.
We're a long way from being Venus
I'd like to think that this is a transfer of wealth from idle hands to productive hands, since I have to assume that at least a portion of the business owners behind those cash machines you mention won't just sit on a montain of money, but rather reinvest it in something. But perhaps I'm too optimistic.
Of course they reinvest it in something. They reinvest it in the same trivial businesses - Farmville, Candy Crush, etc. It's a self-perpetuating cycle of inanity.
I'm not saying games are a waste of time in general, but societies current obsession and normalization of playing them is unfortunate. Same goes for TV, so this started awhile ago, but games dial it up quite a bit.
Mercenaries can be traced back to the 1300 BC and if there weren't mercenaries in nearly every single conflict they've fought in since time immemorial, conflicts and wars wouldn't have lasted nearly as long as they did.
sigh come on humanity, can't we just get along. I know we have to take out bad-apples like Hitler and the 'Nazi high command' but most military actions are often idiotic in nature.
Space needs to be a priority though, we're quickly screwing this planet and we're one space-rock or super-volcano away from extinction (both have happened before, both will almost certainly happen again).
What I'm more upset about is people spending obscene fortunes on Farmville, World of Warcraft gold, Candy Crush EleventeenNinenty4 Now With Extra Bedazzle, Fortnight etc. Energy, agriculture, medical, space are often neglected in favor of the iPad fruit of the month app of the week. It is extremely frustrating.