It's easy to procrastinate when tasks are open-ended.
Deadlines are good at making something a top priority for a short period of time. In addition to focusing energy, forcing functions make asking for help much easier.
By explicitly stating a fixed period of time, people are more willing to go out of their way to help out. With the sense of urgency, they want to be sure they're not the rate limiting factor. As a result, I'm much less likely to need to follow up and ask about their progress. I think this can be attributed to them knowing that the forcing function is temporary, so there's a lower likelihood of mission creep.
It may be tempting to add as many forcing function as possible, but remember this only works if they're out of the ordinary. Don't over use them.