How would you know if they asked for a favor or got their their agenda pushed to the top of the list?  The problem with contributions, like campaign contributions, is that it creates a conflict of interest. No matter what the receiver of said contribution says to defend themselves the perceived influence is unavoidable.

Bitcoin needs to remain decentralized and the way that this is accomplished is making it easy for nodes to decide which version of Core they would like to run.  The problem with this is that most nodes have no idea that it is their responsibility to keep Bitcoin decentralized.  They install the next update blindly.  This puts control in the hands a few developers and if they are funded by anyone there will be perceived favoritism.  Said another way, it becomes a pay to play game like our government has become.

In my opinion Bitcoin development should be strictly volunteer.  Let's not allow the most potentially transformative idea in a generation to be co-opted by anyone.