Main reason as to why Valve's done this was due to a previous influx of c\*\*bots. They were going around votekicking everyone they could find, and even in parties of 6 which would result in them being able to kick everyone. Valve saw this as a massive "attack" and made a quick under-the-hood patch that made TF2's votekick take into account a system that is similar to CSGO's trust factor.

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They've done this before, similar to player reports. These c\*\*bots would go around reporting users - if you played too many games with these bots, you'd get a 30 day matchmaking ban just because they would report you over and over every 3 minutes in every game you saw them in, every bot that was in that game. So they've recently made another under-the-hood patch that makes reporting players useless.