You Get What You Pay For
It might seem like a good idea for those on a budget, but accepting the lowest contracting bid is like shopping for fine china at a discount store. You might find something that'll work temporarily, but you'll end up saving money in the long run by spending more for quality now. Contractors have to make a profit one way or another, so it's not surprising that extremely low bids often involve cheap materials and unskilled or poorly trained workers.
The initial bid could also be a ruse to get in the door. Some wily contractors will even point out the subpar materials they're using to lure you into paying for overpriced premium upgrades. And low bids can turn into expensive jobs after the contractor discovers unforeseen complications.
Don't take out a second mortgage to pay for a job that was supposed to save you money. Seek multiple bids and choose one that's in the middle. Go for something reasonable, but not cheap.