If Regent allows jeans , even on the last night, I think the slippery slope just got a lot slippyer. See not reason that nice cotton docker type pants can not be what is worn on last night. Jeans can be in the cabin to wear the next day to travel and the cotton pants put in the carry on.
Hopefully , Regent will read the comments and rethink this policy. The new dress code adopted a few years ago has worked well , no reason to change it. Just my humble opinion.