Like any large scale software, SB is between the rock of ensuring program stability and the hard place of user flexibility and facilities.
Like providing a decent macro programming facility, universal freezing can easily lead to substantive user f-ups unless the usage scenarios and rules are well designed AND enforced.
There may be several parts to the puzzle that are dependant upon backend facilities in Cubase that are not up to the task as yet.
Several years ago, I suggested that it would be good if the display of channels in the mixer could be controlled by whether track folders were open or not. It would do for pixel usage what freezing would do for CPUs. However, we are only just seeing support for conditional displaying being incorporated into the mixers, which is a prerequisite for fully automating it.
Basically, the ‘fertile ground’ for full freezing may not be prepared enough as yet, but is probably on the agenda for progressive implementation over several releases.