Unless you are old enough and followed the industry trends carefully, many people may misunderstand WHY 4wd became popular, even though its been around for years. It first became popular through the import market, though companies like Oliver had it much earlier. The imports had great little tractors, but when it came to farm duties, they did not have much weight, and even in many cases had poor weight distribution. When 4 wd became popular, it improved the usability of the tractors and their applications. Still today, many of the "import" tractors do not have the same weight as more traditional "farm" tractor brands. Now of course 4wd is everywhere, and people think its indispensable. I like 4wd. I am not against it, and of course, I will still point to weight distribution issues. The problem with 4wd loaders is that people come to depend upon the front to haul the working load. The very people that cite safety are likely to try to back an overloaded bucket out of a hole with all the weight on the front and the rear tires in the air. The little 4wd tractors are especially prone to broken axles and leaky front components, and other issues relating to balljoints and axle mounts because of this. Larger ones are not as prone, but I have seen many a half shaft snapped in two because of poor loader operator skills. (Not to mention raising the tractor off the ground when digging, then slamming the spinning front tires down into the dirt to "bite" in.)
ONE critical issue involved with front end loaders on tractors is turning radius. 2wd tractors typically (unless it is some super steer or something, even then tracking can be off) turn tighter and are more maneuverable than your average 4wd. This makes them great in close quarters. Turning on hills is not an issue in many regions of this country.
My point was that a 2wd loader is better than NO loader at all, and in many cases can perform as good as a 4wd, depending upon the circumstance.