In at least one of my campaign worlds, human magic-users are encountered very rarely. I prefer the mystique of magic items, monsters, and workers of magic shrouded in mystery and spoken of in awe. Most humans have never had personal experience of any of the above, and some may even doubt their existence. If a magic item were discovered, its only viable market would probably be that of kings and rulers of city-states. If a monster were seen, it would probably inspire incredulous terror in all but knights or experienced adventurers. If a known magic-user were encountered, the reaction might vary from swooning admiration to fear to fanatical hatred. Low level magic-users are as rare as earls, dukes, or princes. High level magic-users are as rare as kings or emperors (which is why many of them are employed as highly paid court wizards). Some of them may be kings or emperors. If a magic-user is found undisguised in the midst of non-magical persons, everyone will know that something ominous is afoot, for it well known that magic-users never travel anywhere without some arcane objective.
Due to the rarity and, in some cases, disputed existence of magic-users, magic has not influenced the economy of the world, nor has it altered the boundaries of kingdoms, nor has it affected the lifestyles of ordinary subjects (as far as anyone knows). There are no magic shops where one may purchase magic items. There are no magical telecommunications services. There are no magical rapid transit systems. There are no magical strategic defense initiatives. There are no magically-powered factories. Any and all of the above would be possible if not inevitable in a world where magic-users are as common as they seem to be in some campaigns.
In most of my fantasy games, I prefer magic to retain its sense of wonder, and that means it can never be mundane. When magic happens, stomachs churn and hair feels as if it's standing on end. It becomes something to tell one's children and grandchildren. Troubadours sing of it. A magic-user by his or her very nature is a living legend.
The fantasy in my world is fantastic. One might even say it's fantastical... At any rate, fantasticality has consequences. One consequence is that adventurers will not have a reliable source of magical weaponry, which is very serious indeed when one considers the variety of monsters that are invulnerable to non-magical weapons. Another consequence is that it's deucedly difficult to join a wizards' guild when there aren't enough magic-users in any given area to form one (the absence of which may adversely affect spell acquisition). I shall attempt to address both matters (and any others that occur to me) in the days ahead.