Personally, since I bottle rather than keg, I find that it helps to keep an excessive amount of flocculated yeast out of the bottling bucket and aids in clarification. It also allows me to get the beer into a smaller carboy with less headspace, meaning less risk of oxidation. Lastly, it allows me to add adjuncts like oak and dryhops without compromising the primary yeast cake. For instance, if I wanted to dryhop an IPA, and I added the hops to the primary after fermentation was done, then when I racked it to the bottling bucket, the primary yeast cake would have a bunch of hops in it, preventing me from harvesting it.
Given the ease of racking, I find that it's a no-brainer for everything but hefe's.