The reason why startups are more inclued to do so, is that extra hardware cost almost nothing, compared to salaries. The only reason not to is bureaucracy.
I suspect the reason is at startup the person making the final decision on hardware actually has to use it and is intimately familiar with what's being done on it. At a big org with say 1000 developer's that's not the case and at 1kish savings per machine there's a big "look what I saved us" opportunity for that decision maker.
