I was watching some esport clips and I noticed that some teams do not plant spike after winning, is there a reason for this?

I'm not sure if someone here has already asked this question (apologies if this question has already been asked) but I've always been curious ever since beta, since he's a "shadow" and a "phantom of a memory" makes me question his body buil...

Why do the birthday balloons for the 1 year anniversary do not pop when you shoot or knife them? They should pop. The birthday cake should be destructible too.