Well, the people running La Liga are a joke so it's no surprie they'd come up with something like this.
Stadia aren't being filled up mainly because ticket prices are high and the match scheduling is far from omptimal.
Their policies over the last 10 years have encouraged people to watch the games on TV rather than in a stadium... and now they complain that there are empty seats

The only good thing that might come out of this decision (if it ends up going through), would be that clubs might lower ticket prices so that more people attend games.
Over all attendances aren't that big of a problem in Primera, but in Segunda it's ridiculous... there are some stadia with 10-15% attendances.