Part 95 FRS radios are also required to have fixed (that's non-detachable) non-gain antennas and be Part 15 compliant for EMI and RFI susceptibility and compatibility. Ham radios often have some of this but are only required to keep RF energy inside our bands, if they cause interference it's only your fellow hams to whom you have to answer and at your best operation and engineering practices.
Outside the ham bands radios can't be setting off car alarms or upsetting vehicle computers. Just be sure if you do chose to use these radios for FRS that you aren't screwing stuff up. There are a lot of UHF devices out there, not just radios. Medical RFID devices for example, there is some logic behind the rules in this case since the spectrum around 400-500MHz is probably the most used and sought other than the cell phone bands.
We have quite a lot of spectrum in the band that is under constant threat and finding hams transmitting illegal is one major red flag that will bring the FCC hammer down. It's easy for them to tell, FRS radios have the tailing tones where ours don't and GMRS users have to be licensed just like us. Some of it is already allocated on a secondary user basis, so complete loss is not a remote possibility.
"Why does the U.S. care which flag will be hoisted on a small piece of land thousands of miles away?" -- Ron Paul