It's a larger footprint, possibly drains battery when you don't expect, may mess with signal handlers and other global state.
And it does not really scale to many libraries. What happens when eveyone thinks theor language is best and wants to link in a big runtime? You need 30 different runtimes for 30 libraries? Ouch.
And if not careful about versioning, you could end up with symbol conflicts, etc.
All these problems can be overcome, but are just not acceptable if you want to be a ubiquitous library like libjpeg. Needs to be super simple from a runtime perspective.
