In the the late 80s/early 90s I had a really nice pair of cycling shoes. These weren't clip-in or anything like that, as I rode with toeclips at the time. They were just stiff-soled trainers, very like the Bontrager SSR ones I wear for cycling now (except these days I have SPD recessed cleats in them). Super comfy and practical.
Anyway, around this time I moved house so I put all my various kinds of shoes and boots into a black bin bag ready for moving. I also filled several bin bags with rubbish (you can see where this is going). When I got to my new home I went to extract my shoes and found ... a load of rubbish. The bag with my cycling shoes, waking boots, random trainers, worn out Docs and so forth was on its way to landfill. I suppose it was one way to declutter.
So. Back to the present. Bontrager SSR shoes for the summer, Northwave Celsius boots for the winter.
Are they necessary? Meh. Who cares. For me, yes, because my bike has SPD pedals and my Brommie has flats so I want something that works with both.