Here's my $.02.
The forward assist has a use on my hunting rifles. Numerous times, I've needed to load w/o making the noise created by letting the bolt slam forward. Easing it closed and bumping the FA is much quieter than the rack & slam method. When hunting in snow conditions, I've fallen or had snow laden branches dump snow onto my AR. With the dust cover closed, the chance of snow clogging the action is lessened. With a snow ball packed around the bolt it might work or maybe not but either way it's likely a cleaning will be needed later. But with the cover closed, I'm more confident the rifle will function and I'm not going to have to warm, dry, and clean the rifle after a long day in the snow. The chrome lined bore is optional. I have chromed and non-chromed and Melanite coated but don't see a great advantage among them since I'm not a high volume shooter. It does appear the Melanite may be more resistant to dings and scrapes than phosphate but that's outside the bore and not part of the question.