If you're going to expose it to extremes in conditions and not clean it then the chrome bore is a must. If you are going to shoot it and enjoy it and then clean afterwards don't go with chrome lining. It degrades accuracy a slight bit and is not necessary for the recreational shooter.
Just to amplify:
Sometimes a non-chromed barrel is an economy move by a manufacturer to save money. This is not always a bad thing. If it makes an otherwise unaffordable gun affordable, that is good news for that buyer.
Sometimes a barrel isn't chromed because it is a stainless match barrel. These are usually more expensive than chrome lined barrels. We could have an argument for the next couple hundred pages about whether stainless barrels are inherently more accurate than chrome lined, but suffice it to say that some of the best competition barrels are unchromed stainless.
As VUPD notes, chrome lined can enhance reliability under adverse conditions so a lot of folks make this choice for a combat/defense rifle.