Obviously. But still, I keep having consistently great rounds as Spy, consistently first place by at least 10 points, etc.
Like I said, bad/stacked teams. Consistently makes it even more obvious.
The fact of the matter is that outside of the odd round where the defense is so crap that the traditional point whore classes won't be MVP (medics, engineers, heavies, and demos...especially kritzed demos) thanks to the point bonus granted by backstabs a good team will be killing spies before they get a chance to attack. A spy will die many, many times to random bullshit (stray grenades, stickies, and rockets) and proactive spy checking.
When practically every member of the other team is shooting every teammate to check for spies and there are one or two pyros hunting for them (in my case I regularly use The Homewrecker for my engi brosefs, especially when defending), you're going to have a hard time getting a kill. This is especially the case when multiple teammates have a mic to notify the team that there is a spy, what class it is disguised as, and whether it is using the Dead Ringer (I'll remind my team every time I notice a DR spy get "killed" that it is, in fact, a DR spy).
Sometimes spies can make MVP in generally unfavorable conditions (especially with your typical dumb engies and sapper spamming), but it
should be nigh impossible against a competent team. Spies are most valuable for work that isn't reflected on the scoreboard, namely picking off good snipers, medics (more important when they are close to an ubercharge), and engineers (sometimes cooperating with a demo/soldier to make it safe for them take out a sentry).