Okay look, here's a run down on Vasalgel. There's some huge fucking crap getting said in this thread.
First off, why is Vasalgel even a thought? Because, to be quite honest, birth control pills suck. It's a constant expense, needs to be taken every day, fucks with hormones, and has a variety of other side effects. They suck. Lots of people just don't realize they suck because, even with all their faults, it's still relatively the best option.
Vasectomies are, more or less, permanent, and can be expensive.
So here's where vasalgel comes in -- you have a single injection that, by itself, as a one time thing, provides protection for 10 years. Also, it's completely non-hormonal, so it won't fuck with anything else. There's no side effects. There's no pain (outside of the initial injection, which you guys get fucking shots all the time. Suck it up). You still jizz. Only difference, is that a silicone solution in your tubes kills the sperm on their way out. OH. And did I mention that it is literally as easy to be reversed, as it is to be applied? One solution sets you up for care free inactive sperm for 10 years, and one other injection clears it all up, and a week later you can start pumping for babies.
So between permanent action, fucked up hormones, or a one time needle....
Why the fuck wouldn't you go for the needle?
EDIT: Correction, the "kills your sperm as it goes by" part is applicable to RISUG, which is an *extremely* similar process. Vaselgel actually allows the fluid to pass, but blocks the sperm from leaving. So while all the jizz flows, the "active" part of it stays behind.