It's time to scrap the tube zones

I'm glad I live in Barcelona where I get unlimited travel on all modes of transport for €21 a month :)

This is only in the city and we do have zones outside, but those are mostly for remote suburban towns. The whole metro network is inside zone 1, it stretches even to the airport.

I thought one of the purposes of Zone 1—particularly before the Elizabeth Line opened—was to push cross-city travelers to go around Zone 1, using something like the Overground.

How would this affect season tickets?