Developers (or anyone) buying tools can often also be a sort of local optimization, at the expense of the larger organization. For instance fragmentation, so that you can't find things through a single search anymore, or need to log into different teams' tools separately. Not to mention the compliance nightmare if you want to be SOC compliant while teams are all managing their own tools full of company IP.
Buying books and other learning resources is great, though.
Buying books and other learning resources is great, though.