Suppose there is an upcoming shareholder vote. If my shares are held in street name, and I decide not to participate in the vote, what will happen to the votes that I don't cast? Can my broker use my shares to vote in any way they want?
There is (was?) a NYSE rule that allows brokers to vote in some routine matters when holding shares in street name and shareholders fail to vote. A non routine matter would be something like a merger or acquisition.
Another factor in this is that the company requires enough shares voting in order to have a quorum and broker voting facilitates this.
I offer no specifics and suggest that you google for details.