It’s not just a feel good thing. There are real resource limits, even if someone chooses to foolishly not believe that. If you can get more done with a given level of power and other resources, you get more out of your data centers.
But that's not what anyone means when they're talking about sustainability for data centers in terms of power usage: they're either talking less power (ie less value) or power from renewable sources, which can't compete with sources like gas turbines across a mix of setup time, consistency, and power/$.
If solar and batteries were available sooner than gas turbines, GE wouldn't have a multiyear waiting list. If solar/batteries were cheaper than gas turbines after accounting for land/permitting/maintenance, every DC would be buying the empty land next to them for an eventual switch to solar. Notably these many-million dollar investments aren't doing those things, and I guarantee you they have tried every angle imaginable to get power to the DC as quickly and cheaply as possible.
China hasn’t stopped using coal because of climate concerns. The US hasn’t stopped fracking. Africa won’t stop adding another billion people.
None of those things are going to change because of a potential issue, distributed across the globe 50 years from now.
If it doesn’t make economic sense (at a micro or macro level), it doesn’t happen.