Legacy… many older folk idealize a past that (likely) never existed. Same with Trump voters in the States. What was feels safer than the future, which is scary.

Also the older generations tend to hold on to more of the old traditions, many of which have been lost in China, so they also want to bring that back together and continue the “culture”.

No one is still thinking Taiwan will “take back” the mainland and reestablish the ROC on the mainland. That dream died in the 50s.

Politically the KMT, the party of CKS, officially claims a “status quo” platform now, but many of the older members of the part would be totally fine with unification.