LOB Index || Last_Analyzed Not updated

Hello,
I used both gather index stats and gather table stat for tables having these LOB indexes and still the Last_Analyzed is NULL for them.

select count(*) from dba_indexes i where i.owner = 'xx'
AND (i.last_analyzed IS NULL OR i.last_analyzed < ADD_MONTHS(SYSDATE,-3))
ORDER BY i.index_name;

COUNT(*)

 33318