Being the primary owner of a thing requires constant awareness of the thing.

Constantly asking "is now the time to jump into action?"

Constantly looking out for evidence that some action needs to be taken.

A constant busy loop, refreshing the awareness in your head and asking, "now?".

Whereas being in reactive mode is orders of magnitude easier.

If there is something to do, the world will let you know.

Until that point, out of sight, out of mind.

No wasted mental effort.

There are only a limited number of things you can be a DRI for, but you can be a reactive participant in many orders of magnitude more things.