why are cabinets so small?

So I've never really attempted any plumbing at all.  I can build pretty much anything I'd like to build.  I can fix a lot of things, but I have never attempted messing with water.  I guess I've seen too many 80's sitcoms where the dad ends up getting soaked under the sink because he has no idea what he's doing. That all ended today.  We bought a reverse-osmosis water filter last week in an attempt to help our daughter with her eczema and allergies - we've read in a ton of places that some kids get a lot better when chlorine and/or fluoride is removed from the water.

This was a pretty serious operation in my book and I think I nailed it!  So far, no major leaks and the system works like it's supposed to!  I'm quite proud of my work here, but I do have a question about modern home desins.  Can't someone create a cabinet for under the sink that has more room?  Holy Cow it was tight under that sink!  Anyway, a post is always better with pictures, so take a gander at my handy work.  Ok, now that I've spent this time bragging, I've gotten paranoid that it's leaking like crazy...I'm gonna go double check!

The part I was most nervous about was drilling a 1/4" hole into a perfectly good drain pipe!  I was extra careful to only drill through one side of the pipe!