Those giant grinders are obsolete and the old wheels on them are "widow makers".
Agree, a large, powerful belt sander is a wonderful thing to have.
Re; Old grinders. Your opinions are allowed to vary, but sixty years of experience disagrees with your flat statements.
That the big dogs still sell for good money is proof not everyone feels they're obsolete.
For example, home shops come in all sizes of workpieces. If one does much steel fabrication, a wheel grinder will shape workpieces. bevel edges and clean up welds, the rough edges of which can rip up belts.
Again, one is working on rusty old car parts, a 10" wire wheel on a large grinder will remove rust on large parts quickly and easily.
Ideally, one would have several sizes and powers of stock removal equipment.
Jack Vines, who has a dozen small and medium bench grinders and a couple of belt sanders and should sell some.