Well, that's part of it. Adaptec expanders are not popular, and Adaptec HBAs (including RAID controllers) are known to not work well, to put it mildly. Despite conscious efforts to move things along, they just did not care enough to fix their drivers.
Meanwhile, LSI expanders are mostly trouble-free, with the most relevant issues being compatibility quirks between SAS3 and SAS2, which were fixed by firmware updates years ago.