Oh come now. Surely you're exaggerating a bit. All games are not sandbox games. Chess has an end goal to it, and so do most other games. Then there are games whose point is entirely to accumulate score - as much score as you can achieve in three lives. Surely if you've been playing computer RPGs since the mid eighties, you're old enough to remember going down to the arcade and stuffing quarters into Asteroids and Gorf and Galaxian and Gauntlet and the like. None of those were sandbox games.
Nope. Never played arcade games. NOT my thing, mindless - just like slot machines. All games (even board games) exist to provide fun for the players. Some of them are more "directed" - but those are outside the field of RPGs. And I'm not about to get into an argument over it.... I have played every CRPG without doing the MQ - on at least some characters. Actually.... hmmm. I never did the MQ in BG.... eww.
fenrir: I have various toons in various stages of "development". Some of them are melanges of stealth, magic, and combat users. Others are "pure" types - like a "pure" Breton mage, and a "pure" High Elf mage; a "pure" Nord fighter, and a "pure" Redguard fighter. I play them to see how they differ as to the challenges in game. It just depends on what floats your boat, you know.