If you have a 0.0000001 output but it would cost 100x as much in fees to spend it would you spend it?  Of course not.  Kinda like mailing a penny (at a cost of $0.46) to your bank to apply to your mortgage principal.  Nobody does that it doesn't make economical sense.  So these uneconomically outputs are likely NEVER going to be spent.  Each one that is produced won't be spent and thus won't be pruned and will remain in the UXTO forever (or a very long time on average) this is causing the UXTO to bloat and will continue to bloat as there is no reason for anyone to ever spend these outputs (and spending is what allows an output to be pruned).