reasons:
During VSH when Hale taunts and stuns nearby players, people can just do sm_thirdperson to toggle back to firstperson, ignoring the stun
Avoid enemy tauntkills suchah Huntsman/Holiday Punch
Can skip some seconds on taunts suchas Buffalo, as after mini crits are gained a person can quickly toggle it to firstperson to skip the very few seconds (that do matter) during any heavy boxxing match, or anything that does this aswell, like the Crit-A-Cola/Bonk!/Sanvich/Amputator
Skip taunts. Say if I miss the kill with the Spy's Knife, I can quickly skip a few seconds so I'm not backstabbed/killed