They're just not stable enough. They tend to splash or fall over if they're big etc etc. Also a funnel doesn't eliminate lifting a 40lb gas jug up to shoulder height in leathers. This is just very easy and was cheap and requires zero maintenance and all that.
I use these HF pumps, yes I am cheap but they usually last a year for less than $15, just keep several on hand.
How about pumps for emptying gas tanks? The ones with the long straight piece don't work, and a simple siphon doesn't get it all. Any suggestions? Got three or four gas tanks that need to be drained.
The one @Mongo listed above will pump most out. Also available on Amazon. One year warranty, and they honored it without any qualms whatsoever.
How long do the batteries last? If I have to start stocking AA's in my kit, it's a non-starter for me.
The Tera pumps can be modified to run on power tool batteries. Ours runs on a Milwaukee m18 fuel that we need in the pits anyway.