I had a buyer ask me if they should get an inspection on a new home, even though it has a one-year warranty?

Yep, you should , for four reasons.  First, a home is a cooperative effort of a dozen building trades -- plumber, framer, concrete company, electrician, finish carpenter, roofer , floor covering, tile layer, painter, heating and air  contractor and a coupla more I forget right now. 

While the bigger pieces, such as plumbing, wiring, framing and foundation, are subject to being inspected by building code enforcement, supervision of minor sub-contractors is up to the builder and even the best builders can't look over all those shoulders all the time while they're working.

Second, the true test of whether all these mesh together correctly won't occur until the first days and weeks that a house is occupied.  It's very rare, indeed, that something doesn't come up wrong during that time.  Some of it may be seasonal -- the new owner moving in winter may not find out until summer that the air conditioning doesn't work.

A responsible builder will honor the warranty and respond to problems within the first year.  Most builders are one-person operations, though, so the builder could have decided to retire or quit or get a job with better hours and less risk.  Consider also that once a house is sold and the builder has his money, the new homeowner has little to no leverage to get the builder interested in coming back.

The exception here may be national home warranty programs, some of which I'm told are reasonably good, although I've had no personal experience with them. 

Third, the average new homebuyer isn't going to have the experience and knowledge to truly test a home's systems and structure prior to borrowing all that money to bpay for it.

Fourth, if your home inspector finds a problem between the time you've agreed to buy a new home and the  time the deal closes, the builder is gonna jump on it like a starving dog on beefsteak, 'cause that problem is standing between him and getting paid for the house.  

So, yeah, hire yourself a good and reputable home inspector.  They're not that expensive and it's cheap insurance against buying a problem, along with buying a new home.  Good luck with your new home.