I would say it's very natural for humans to do some grooming, and when people stop altogether it can be a sign of mental illness.
What is expected in terms of grooming is largely determined socially. What we find pleasing to the eye and expect to see. It's also pretty normal for special occasion grooming to be more complicated or just different. That's not necessarily a problem.
Sometimes however the social norms can become dangerous or burdensome, and it's worth it IMO to be conscious of it and try to push back.
Anything unhealthy like a lot of the medical cosmetic stuff now should be right out, IMO. But I think it's also worth thinking about it when the time commitment and cost begin to climb.
Part of that is also understanding that for many things, we are always going to have some social expectations attached, so the idea that individuals will opt in or out by personal preference is a bit naive. Our preferences are shaped by the environment, so many people might accept that something is needed only because they are used to it. If we stopped doing it, we'd soon not notice.
For me, hair colouring falls into that a bit. The idea of covering grey has a lot of appeal to many, but as a result of it becoming common, we now have a really unrealistic sense of how people age. When we see someone in her 30s with more grey, which is really quite common, we tend to overestimate age, for example.