It was supposed to be for aging old people who were forced to move because they couldn't afford the taxes as their homes increased in valuation.
But commercial was also included, with the thought that lower taxes would let landlords pass the benefits onto the tenants.
But they never did, they just pocketed the savings.
https://en.wikipedia.org/wiki/1978_California_Proposition_13...
In addition, commercial properties would be owned by immortal corporations, which would change hands without reassessing.
https://en.wikipedia.org/wiki/1978_California_Proposition_13...