To answer the headline, we stopped caring when a bunch of off-the-shelf solutions became available.

For a lot of problems, once you have this off-the-shelf solution, you're just not going to have a memory issue. It's like cooking without having to manage where the pots, pans, and plates are. Say you hire some guy to clean up for you, and the guy just implements some simple strategy. It's a lot more pleasant, and if you have a large enough kitchen, it won't make a difference to the quality (and timeliness) of the food. In some cases you may have to consider the guy running around, but most of the time you net win anyway.

For things that are truly performance sensitive, you still need to think about cache issues and such, and you definitely still care about memory management.