Grapples aren’t cheap. If that’s the only thing you need a third function to run that adds substantially to the cost as well. Brush, logs, debris, and large rocks can all be moved with bucket and/or forks.
When the topic of grapples comes up, I’ve seen many, many threads where various folks who don’t have a grapple extoll the competency of forks and buckets for moving brush. Have never seen a post saying the poster has both grapple and forks, has moved brush with both, and found the grapple to be only marginally better than forks therefore grapple was a waste of money.
Whether a grapple is worth the money or not, like many implements, depends on how much you’ll use it. If you have a little bit of brush or debris to move, forks, bucket, trailer, pickup truck, or all manner of alternatives may be reasonable. If you move a lot of brush or debris a grapple is worth the money.
You can change a wheel on a car with a tire iron or an impact wrench. Both work perfectly well. Which is truly the appropriate tool depends on how often you change wheels (tire shops seem to prefer impacts) and personal preference. However, if you think a tire iron is as good as an impact at dealing with lug nuts, or forks are as good as a grapple at dealing with brush and debris, you are incorrect; likely due to lack of experience with both options.
For moving logs, a grapple is also better than forks or bucket, but the margin by which it is better is less than it is for brush and debris. In situations where the log is downslope from the tractor, loading onto forks can be challenging whereas a grapple can grab the log regardless of slope. Also, a grapple can grab a log from the end to pull it lengthwise, turn it, reposition it as needed to pick it up or get it somewhere it can be worked up further. In near ideal conditions such as a logging deck, forks work nearly as well as a grapple at moving logs. The more challenging the situation, the more the grapple out performs forks.
Yes, I have grapple, bucket, and forks. Have moved brush, debris, and logs with all three. While they all three work, the efficiency of the forks and bucket is in no way even close to the grapple. If moving moderate amounts of brush and/or debris occasionally, I’d probably just use forks and save the cost and storage space taken by a grapple. If you have a lot of brush and/or debris, or dealing with it is routine, a grapple is very much worth the cost.