Use A Vocal Booth For Isolation
Probably the biggest reason to get a hold of a vocal booth is isolation. For example, I was reading in EQ Magazine about how the Red Hot Chili Peppers recorded their last album at Rick Rubin's living room. (I'm not sure I would call this “home recording” necessarily”). They wanted this album to have a much more “live” feel some of their other records. They wanted to sound like a band playing as a unit in the room without a dependency on overdubs.
For the singer ,Anthony Kiedis, they brought in one of those portable vocal booths that you always see advertised in the back of recording magazines. Why? Well, because the drummer was about 10 feet away! There would be more drum sound in that microphone than there would be vocal sound even when considering the cardioid pattern of the Shure SM7 microphone.
In order to keep out not only the pounding drums, but also the bass and guitar, they elected to use a vocal booth right there in the middle of the room. This made it easy to keep the live vocal. This also makes it easy to do overdubs. You see, when you record with lots of bleed into your vocal mic (which certainly can be a good thing)and then want to overdub a few words (no bleed, the band already went home) it is sometimes a noticeable change. Using the vocal booth allowed them flexibility.
Of course, if you do not record keeper vocals during drum tracking, this won't help you much. If you are working with singers who require a lot more producing / coaching, the odds of keeping a live take are slim. I've only done one project where I recorded a band live in the studio where we kept all the live vocals. Most singers aren't up to this level.