Though tristate logic issues can be fixed in DFT, it still reduces the test coverage and requires effort. Also, it's not recommended to use tristate logic because nobody can be so sure that the logic is perfectly correct that prevents bus contention from happening on these tri-state buses. When none of the tri-state buffers drives the bus, the bus is somehow floating, which causes huge power consumption. To resolve this, designer should put bus-holder or logically guarantee there's always at least a driver. And .....
In short, no one would like these troubles...