Here in Washington on the passes, most of the time when chains are required, all wheel drive vehicles are exempt. However, you must have chains with you even though you don't have to put them on. I've never heard of anyone getting spot checked for this, but something to consider.
There was one day last winter where chains were required for everyone crossing Snoqualmie Pass including all wheel drive vehicles, but that is the only time I can remember in the last 20 years and it had snowed 18 inches in one hour. Usually they close the passes when condition gets that bad.
Having said that, if you do get chains, make sure you can put them on and take them off at home so when/if you do need them, you aren't trying to figure out how to use them on the side of the road and in the snow, or worse, find out they don't fit at all. Every time I've ever put chains on a vehicle, the weather has downright sucked with heavy snow, wind, and very cold.
Chains are really just another tool or safety device to have with you when traveling in the winter where there is frequent snow. Hopefully you won't need them, but there if you do.