I have friction shifters and simply can't see any reason to "upgrade" to more finicky indexed.
I can switch to a different rear wheel having a different number of cogs and only have to adjust the limit screws. That made for a relatively inexpensive upgrade from a 7 to 8 speed rear. If I wanted to go to 9 speed, it's just a matter of a new cassette and a chain. My shifters would still work fine!