Buying a macro lens is useful for a lot of photographers in a number of different genres, however, it's a difficult purchase to justify if you do not do much macro photography specifically. If it had some other purposes it would be a more palatable purchase, and if you take any portraits, it does have.
Coincidentally, my first macro lens was a Canon 100mm f/2.8 from the 1990s that I have discussed on a few occasions. It didn't cost very much, but I didn't have much to spend and so it was still a large investment for me at the time. I loved macro photography and it made up the bulk of what I shot as a newbie, but I did want to try my hand at lots of genres, and top of that list was portraiture. I had the nifty-fifty that every photographer buys and that was great, but I wanted something longer.
I can't remember how long it took me to try out the 100mm f/2.8 macro for portraiture, but I suspect it was around the time I started investigating the switch on the side of the lens that allowed the full distance range for autofocusing, not just the macro ranges. 100mm is a great focal length for portraiture on full frame and offers a pleasing compression of your subject. While f/2.8 isn't the widest, when paired with that focal length, the subject and background separation is superb and with the right lens, the bokeh is attractive too.
In this video, Alex Barrera goes through his recent purchase of the Canon RF 100mm f/2.8L Macro IS USM and how it doubling up as a portrait lens helps offset the financial outlay on a new macro lens.