Cause then they have more space to actually make their own design with rather than everyone having similar heatspreaders with a different sticker.
Also for people that watercool (whether custom or AIO) the height of the RAM does not matter, but it also means there's less airflow around the CPU socket area so, while probably still not absolutely necessary, it can be nice to have to more efficient heatspreaders on your RAM.
Don't know, they certainly don't seem to be among the biggest players (imo Kingston, Corsair and G.Skill). Last Mushkin I've had where the limited edition Charcoal Grey DDR2 800 ones - never regretted them!
The height of these new moduls ins't too bad as compared to Kingston's HyperX Predators which are massive - and pointless whereas cooling is concerned (they don't get hot anyway)!