Roleplaying outside of combat requires spells? That's a new one on me! Maybe it arose during the 3E era, when from what I saw the vast majority of characters (assisted by the class-mixing rules) were at least tyros at spell-casting -- and the broader notion that
anything worth doing was done with number-crunching and dice-rolling was gaining traction.
Miniature figurines per se are not required in any edition, but 4E very clearly and strongly assumes a square grid and markers of some sort. The 3E rules were also, but perhaps more weakly, geared to that setup. The default level of abstraction in old D&D more easily accommodated tactical play without such apparatus.
D&D Volume 1 said:
The use of paper, pencil and map boards are [sic] standard. [The last are for wilderness adventures, Outdoor Survival being recommended for impromptu ones.] Miniature figures can be added if the players have them available and so desire, but miniatures are not required, only aesthetically pleasing; similarly, unit counters can be employed -- with or without figures -- although by themselves the bits of cardboard lack the eye-appeal of the varied and brightly painted miniature figures.
The first edition
Dungeon Masters Guide at pp. 10-11 suggests, "The special figures cast for ADVANCED DUNGEONS & DRAGONS add color to play and make refereeing far easier." Of the Grenadier Models line, it states, "These figures are the only ones which comply in all respects to AD&D specifications and the AD&D MONSTER MANUAL," and urges, "Always look for the name, ADVANCED DUNGEONS & DRAGONS, and the TSR approval mark before purchasing figures for your campaign."
That last "word of warning" to use only OFFICIAL or
Authorized products appears three times in half a page! One may consider whether the existence of an
in-house line of figurines has any bearing on game design.