Some may recall that WotC made note to point out the common presence of crossbows in the preview art for 3E.Because having your wizard cast a spell is more fun than shooting a crossbow, for most people.
but Barbarian is here as a new martial class.
I think that there is the realization that in game play people want to do more than just hit point attrition and the least controversial way of doing that is "spells", because "magic".
It's been a few years since the Barbarian was new....
And for some, it isn't even exactly that it is "more fun" - just that there are two options available, and it seems like there is no reason not to go with the second option.
For clarity, these are the options I speak of:
1) Make characters that focus on magic use (i.e. wizards) use non-magical means more often than they use magical means.
2) Make characters that focus on magic use (i.e. wizards) use magical means more often than they use non-magical means.
Assuming, of course, that the two options result in mechanically similar game impact (which, oddly enough, isn't actually quite the case given that old versions of the game expected the caster characters not only to not use spells as their go-to method of action, but to use weapon attacks when your choice of weapon and chance of being successful are both signifcantly lower than any other character's - meaning the old style isn't just "magic doesn't happen so often" but "characters that primarily focus on magic spend a lot of time with terrible chances of successful contribution to a significant portion of the typical game experience." And with that being the case, it's really a "no brainer" that people would prefer the modern "my character actually gets to do something" style).
And for some, it isn't even exactly that it is "more fun" - just that there are two options available, and it seems like there is no reason not to go with the second option.
For clarity, these are the options I speak of:
1) Make characters that focus on magic use (i.e. wizards) use non-magical means more often than they use magical means.
2) Make characters that focus on magic use (i.e. wizards) use magical means more often than they use non-magical means.
Assuming, of course, that the two options result in mechanically similar game impact (which, oddly enough, isn't actually quite the case given that old versions of the game expected the caster characters not only to not use spells as their go-to method of action, but to use weapon attacks when your choice of weapon and chance of being successful are both signifcantly lower than any other character's - meaning the old style isn't just "magic doesn't happen so often" but "characters that primarily focus on magic spend a lot of time with terrible chances of successful contribution to a significant portion of the typical game experience." And with that being the case, it's really a "no brainer" that people would prefer the modern "my character actually gets to do something" style).

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.