"why you wouldn't just increase your NAS size is beyond me"
Because a lot of IT teams don't have the capital budget, rack space or staff to constantly keep adding additional capacity.
even though you say that, I know from experience, managing a storage array on a daily basis (and this would consume a substantial amount of your day), if gets old and boring very quickly.. after 2-3 months, you'll be left begging for a set and forget solution!
