The brakes use hydraulics to help them along in modern cars (the big round thing with pipes goin in).
Unlike springs, hydraulics need to be pushed and pulled so to speak, So if you push (brakes on) somthing needs to "pull" them back off.
The vacuum hose from the engine (vacuum pump) does this. I supplies a little negative presure to the master cylinder to release the brakes.
If the vaccum is poor or not working then the brakes may stick on completely or be very poor to respond. This can result in wearing out pads and discs super quick, blowing the master cylinder seals (not cheap). Best to get it checked.
Remember any fault to do with the braking system should be treated with caution and properly inspected and repaired! Dont bodge it!
Altho.. using it to hoover the car sounds good!!
Hope this makes sense.
Many a master cylinder going and many vacuum pumps on tatty ratty landrovers!