I agree with you in principle, but speaking from strictly a strategic perspective, /r/place presents a vulnerability that can be exploited without contributing what Reddit really needs to regain its status - content.
In the context of a social media war, this means we can use the space to peel off users who wouldn't have been introduced to the Fediverse otherwise, with no risk of harming ourselves or providing Reddit more than a temporary moment of attention. There's been a concerted effort to remove links to Fediverse resources in many subs, and for a great deal of redditors, they're in the dark about what the Fediverse represents and how much better it is than Reddit.
Plus it's just cool to fuck with Spez, and the Fediverse is so cool in general that I'd love to see what the effect would be if we united against a common enemy.