Well in my KM school we train sparing at full speed, at first with low force and later with full force. In my school you can pretty much decide the strength between the partners. We do use boxing for that mostly though (added kicks, chocking etc.) Same goes for dodging and moving, we are using boxing techniques for that.I do agree though that most MA centres have way to few "real" fights.
Also you might speak for the U.S. but here good boxing gyms are just as expensive as KM. All about 30-45 Euro.
Boxing does however restrict yourself too much in my opinion. In many situations elbows, knee kicks, kicks, headbuts are a better solution. Also boxing doesn't offer defence for those above, choking or grabbing attacks. Adding to that in boxing you are in a safe place with one enemy, enough light, good shoes which is totally different to a situation in which you don't see much, the enemy has a weapon, there is loud music or whatever can confuse your fighting. We train all those situations (and many more like cars, busses etc.) in KM.
Also no doubt in a fair one on one fight I loose to a boxer. But I'm not training for a fair one on one fight.
Oh and I don't go training to go up against the toughest kids in town (though I probably do considering the amount of soldiers and military instructors). Training against weaker, stronger and equally strong partners makes a pretty good mix. Even girls are allowed to train with me