It really varies between worlds. In FR thier are tons of powerful villians, but they limited in influence by other powerful forces both good and bad. Think the cold war idea of mutually assured destruction. People turn to advanturers, because who else would be stupid enough to do that sort of work.
In Eberron magical war almost destroyed them, its why no one wants another war.
Athas, magic costs too much to abuse recklessly.
I will say most practical useful magic tends to be divine or Primal. Magificent manion, permanacy, polymorph any object and wish, and divination spells being the only non combat magic that would be useful in day to day off the top of my head for wizards.
Clerics got healing, summoning food and water, light, heal wounds, cure disease, blindness, protection from element, magic to keep your dead well dead not undead, verious wards, ressurect, animate objects, mend, miracle, water breathing, ect... If its practical magic odds are your going to see a cleric or some other divine class. Plus clerics are usually more common then wizards.
It actually makes the role of religion and its interactions with the state more interesting.
Think about it your kingdom may have some wizards on staff, but mostly in the army as advisers or adventures. The churchs are who you turn to for most advanced services. You don't need magic for dung sweepers, but you'll want the churchs to handle your fire department, healthcare, help with defence, help with criminal investiagations, and fight starvation, and more. That's in addition to non magical stuff like birth, death, marriage, divorce, records, and other duties depending on the church. Oh and thiers multiple Gods. If you thought the middle evil church was powerful, it'd be nothing compared to churchs in say FR.