As surprising as it may be, there are two reasons for this...
1 - the PPL syllabus no longer requires spins to be taught, so some FIs may not have done a spin for a while - if they are not comfortable, then best not to
2 - not all school aircraft are cleared to spin, e.g taper wing PA28s.
Back to the thread, I started on gliders and enjoyed every minute - I also learned what rudder pedals were used for