A lot of people seem to misconstrue the purpose of this addition for some reason; mostly because they have their own agenda of victimization to perpetuate. For the record, it's not about "catering to the casuals" i.e.: Bads". It's about trying to recreate the far more active raiding scene from Wrath that's largely died out with the launch of Cataclysm for various reasons - primarily the loss of gear prestige from 25 man raiding.
It was that gear differential the encouraged a lot of alt raiding amongst guilds who often couldn't field a second full 25 man roster to attack the raid that week. That lack of personnel "in house" created a whole lot of opportunities for the people with limited play time to simply log in and go hit a raid because Trade would be actively spammed during the evenings. Now, with 25 man raiding diminished and 10 man raiding on the rise there's a lot less action on Trade looking for groups - 'specially once you're off the high pop servers. In addition, a lot of those Trade groups are looking to fill 10 slots, with DPS often filling quick and Tanks/Healers being the only things in demand.
So, the people with no interest in guilding up or unable to meet raid times frequently find themselves locked out; left with little to do once they've Heroic Cap'd and few reasons to log on until the next patch. Raid Finder exists address that need and it's a benefit for everyone. People in your guild who can't make raids for some reason (say, a work schedule shift),now have an avenue to keep up somewhat on their spare time so they're not as far behind when they can come back to the roster. New players get to sample raiding and, perhaps, get an itch to try the full blown thing which brings in fresh blood. Time limited players get their Wrath raiding levels back so they don't walk away and lower your server pop/drive up the economy by stopping to gather things needed for raids.
Someone else can likely come up with more but those alone are reasons that make the RF worth having regardless of your personal stance on who's "wrecking the game".