I am glad you are off the fence. It must have been uncomfortable up there
First of all, they are not baby seals. They have to be at least 1 year old, and can not have their white fur. This applies to commercial and personal hunting of seals.
Why use a club? Well I will first explain to the best of my ability the personal side, and the commercial side.
If you are of the Inuit, or other tribes of Alaska and Canada in the coastal areas. You are not going to have a lot of money, especially if you live the traditional way. A device that uses an electrical charge is far to expensive, and ammunition doesn't come cheap. A club can be made out of anything. Also tradition comes into play. They have been doing this for 4,000 years, if they found a quicker and more humane way to kill seals, they would have found it already. Trust me, the native cultures all around the world hold great admiration to the animals they hunt for food and accessories. The Ojibwe people refer to every animal as brother, and they have great respect for the animal they killed because it has given up it's life for them. The Inuit who club seals are not cruel heartless people just there to kill animals, it is part of their culture, and they go about it very carefully as to cause the least amount of pain to the animal.
On the commercial side, they probably have a better way to go about this I just haven't read into it enough. I don't really know the figures on how much seal meat and skin are going for, but if it is a pretty good ammount, then their should be some R&D in some sort of quicker, more efficient and less painful way of killing seals, while being cost effective also.
Who knows, maybe the club is the best way to knock these seals out.
The one thing I know for sure, is the animal rights activists have blown this (as they have with everything else they do. I'm looking at you PETA) way out of proportion.