Service and lakc of gear availability atre the main issues. They can be tricky to work on if major service is needed, like say a U joint or front seal. As far as people swapping out for open drive, usually it's in concert with a non-torque tube compatible trans (like a 5 speed T5), or use of an engine/trans combo that won't work with it (350/700R4), or, in most cases, just rying to get a better ratio than stock with as little cost as possible. Many times, it's a combination of the 3.
