I remember when I ran AD&D (1e and 2e) back in my college days clerics were rare as PCs. If the party was lucky they had a Paladin with his laying of hands ability and a crap load of potions. Magic-users weren't much more common, and once I banned Bladesingers from ever again being used in our group, I'm not sure we ever had one again.
It certainly made writing adventures for the group a bit of a challenge, as the party was built more for head on combat than it was stealth or death from afar. I also found myself using less NPC spellcasters, for the few I used were damn tough on a party that lacked a response. Remeber, the goal at the end of the night is for everyone to have fun.
In the playtest of The Unmaking Campaign, we lake a magic-user. So, no sleep spells to save our bacon. No web, invisibility or fireballs as we rise in level. I doubt +Jason Paul McCartan is going to change the campaign to conform to the PCs - this is, of course, a playtest. Instead, it will force us to overcome out shortcomings.
So, how important are PC spellcasters in your campaign?