reclaim space in an index tablespace

I have Oracle rac 19c on linux 7 with 2 nodes database 19.3

i have 1 tablespace for indexes for a schema on another tablespace,

the schema tablespace is being cleaned and storage reclaimed after i issue alter table drop partition update indexes on regular basis, after this is run only the schema tablespace has storage reclaimed while the tablespace containing the indexes is not

why is the storage not reclaimed from the index tablespace knowing that the tables the partitioned are dropped from has the biggest indexes

Regards