An interesting question. This article lays out just what the Speaker does. How he or she is elected. And the rest of the party big shots. What the Speaker Does: In addition to presiding over the House, the speaker administers the oath of office to new members, signs bills and resolutions passed by the House, and appoints members to committees. The speaker also recognizes members to speak or make motions and declares quorums. I think the highlighted part is the most vital. It's a form of bribery and loyalty chains. You want a nice, juicy slot where you can get goodies for your constituents, do what I tell you to. As has been shown, go against the Speaker and one loses a committee assignment. Read more @ Why Does It Matter Who the House Speaker Is?