We have had some teams of clients shooting here this year, one of which decided against having loaders as they were shooting single guns. After the shoot when they visited the factory they asked if they should have had loaders, I said they should have. The loader is your partner for the day, he will of course do his job which is to prepare your guns, come fully laden with cartridges ( it is a sin to run out), load your guns be it a pair or 'stuff' if you use a single gun ( you open and eject the cartridges and he will put 2 more in, much quicker than fumbling for your own ), after the drive is over he will collect the spent cartridges and leave your peg clean and tidy and finally at the end of the day he will thoroughly clean and pack your guns.
On top of all these jobs, your loader will be your companion for the day. He will be doing his very best to ensure you have a great day, he will be quiet if you want and just get on with the job or he will give some advice, where the birds will come from, how high they will be and other knowledge from having been on the drive many times before. If you are having a poor run he is possibly be able to give advice and encouragement ( many are very keen and proficient shots ) and if you are doing well he will certainly be congratulating the great shots that he does see between loading the guns.
The cost of all this service is the same as 2 birds so is realy not worth thinking about, a no brainer as they say. You have a better shoot and there are more enthusiastic people employed by our sport. So if you come to shoot and are offered the option, I suggest you take it!