When hiring a contractor for your renovation or building project a good practice is to get three competitive bids.
In my opinion as an informed consumer you should not even consider a contractor to submit his proposal without seeing a certificate of the proper insurances. Liability insurance is very important but you should also require workers compensation with any competitive bids if there will be employees of the contractor or subcontractors present. Generally a contractor that fails to acquire these necessary insurances will always be able to estimate a project less expensively because they lack the cost of these insurances. In this case less expensive is definitely not better, and surely doesn’t make for a competitive bid!
Any contractor serious about performing quality work would never even consider doing business without proper insurances.
If any unforeseen accidents occur “ie” electrical fire from improperly installed wiring, or a flood from improperly installed plumbing you would be left holding the bag hoping that you homeowners insurance will cover the damage. Even if they do you could possibly see an increase in your insurance premiums! Worse off could be in the event if one of the contractors employees or subcontractor got hurt at your location, you could find yourself involved in a lawsuit to cover medical expenses which should be covered by your contractors insurance!!