The oil filter can sit right on the floor, it can take the weight of the AK. If you have a gas tube that doesn't come off, it's an advantage.
1. I can't tell if you're playing devils advocate or if you really believe that there's no cheaper way to get the same effect and that it's necessary to spend $75 to keep from making a mess.
2. Have you ever heard of "constructive possession" and have you considered how that concept would apply to having such a device along with a firearm to which it can be attached?