I dont know what you talk about ? D&D never was a low magic setting, like for example DSA ("Das Schwarze Auge", not sure how its called in english - "The Black Eye" ?!?) is.
In D&D you CAN definitely "just walk into a store and buy a magic sword". Thats all over the system, and settings like the Forgotten Realms. Sure, it doesnt work just in any small village, but if you get to large cities, you definitely can just buy magic items, if you have the necessary coin.
Personally I far prefer high magic settings.
