Is there ever a time in which Yo is needed?
Yes: when you want to stablish the difference between what you do, and what others do (like in "I, for one). This happens when you want your audience to consider in your sentence some other people and you, all at the same time, but as belonging to potentially different groups. "Yo" is some sort of "I don't know about the rest of the people, but I of one...". Also, once established that contrast, further clarification is unnecessary and redundant, so it should be avoided.
Just imagine this text:
I, for one, have enjoyed my holidays, and I, for one, went to the beach everyday, and I, for one, got tanned, and I, for one, did a lot of sport.
These "I, for one" are not grammatically wrong, and surely you want to say "I, for one" under some circumstances, but not all the time. That's how we feel when we hear "yo, yo, yo, yo...". Why do you say "I, for one" all the time? One may ask. Why do you want to say "yo" all the time? We wonder.
"Yo" can also be used if the verb form is identical for "yo" and "él", and the sentence could be easily make sense either way. Here, "yo" is used AGAIN to call your audience attention regarding the "I" vs "not I" distinction.