There's the aspect of why you would choose to replicate a particular study instead of doing something else - there's always more ideas than your ability to execute them.
At least for me, there are two cases why I'd bother to do that and why I could write in a grant proposal that this work is necessary - either I want to build on that study; in which case most likely I wouldn't publish just a pure replication but rather a comparison of my changes with my replication of the original study, and this paper would be counted as a novel study. Alternatively, I'm doing a replication because I'm not certain whether the original study is actually true, because I have some solid reason to believe that it's wrong.
Possibly yes, someday, if they're still relevant. I mean, not every paper even deserves to be read, there's a lot of garbage published somewhere with an imitation of peer review. There's a lot of publications that have never been cited and likely won't ever be, much less replicated.
As I said before, at any point of time in any scale of research the next research steps that "need to be done" vastly outnumber the resources to do it, so obviously not all of these things can be done. The majority of reasonable grant proposals get rejected, so that research doesn't get done - it's all a matter of prioritization; unless there's solid argument that this research task is within, say, the top 20% of the important research tasks, it won't get done. And most studies are not so important to justify repeating the effort; perhaps it was justified to expend X resources to get to that result, it doesn't necessarily mean that it's worth to spend 2X resources to get to a slightly more certain result after replication. It only needs replicating if lots of people are going to build their research on top of these results, and that simply doesn't happen for most studies.
At least for me, there are two cases why I'd bother to do that and why I could write in a grant proposal that this work is necessary - either I want to build on that study; in which case most likely I wouldn't publish just a pure replication but rather a comparison of my changes with my replication of the original study, and this paper would be counted as a novel study. Alternatively, I'm doing a replication because I'm not certain whether the original study is actually true, because I have some solid reason to believe that it's wrong.