[bkbleikamp]

Why should internal tools be ugly? Well designed tools help people work better and more efficiently—putting a little bit of thought into them is not a waste of time.

[ceejayoz]

It also instills a "just because only a few people will see this doesn't mean you can half-ass it" attitude.

[RivieraKid]

And even if it doesn't result in higher productivity, it would be a often a good thing to do, because it makes the developers' work more pleasant.