Legal hurdles. Each of those unneeded libraries will have a license which needs to be analysed by corporate lawyers to check if they've nothing in them that can come back to bite you (for example something sneaking in a GPL like clause requiring the sourcecode of everything using it directly or indirectly to be donated to the creators of the library, I've seen weirder things myself).<br/><br/>
If you're creating your own application to work on resource starved devices you may also have very strict limits on the diskspace and memory used by your system, in which case a few megabytes of spurious libraries required by a 3rd party API may well mean you can't use it at all. |