An endless selection of plumbing parts. Whatever I need, I'll find it here. Often I only have a vague idea of how I'm going to do something, but being able to search through these shelves and dry-fit parts together tends to unlock solutions I hadn't even thought of.
Then there's also the immense calm I feel being in a space where everything is neatly organized in its dedicated places.
As long as your enjoying the work and make it look good. Rule number one, make it look sexy. Just a difference in view points:
For one, pex is generally a cost effective option. Those fittings probably cost 10x the pipping. Also a general plus of Pex is ease of installation. Lotta time using compression and leak testing. Also compression isnt used behind walls or unaccessible locations. And lastly to remove a fitting all you need to do is snip it off with a tubing cutter. Pex is a great product and has many benefits/ special use cases but for cost and ease of installation as a major reason.