I can't live with the tiny enter key on US/UK layouts. I've spent way too long on the big one :)

Also US and UK aren't in the EU, so shipping and taxes are going to literally kill me.

UK layout has a big enter key and small left shift; it's the US layout that has a small enter and large left shit.

Ireland uses the UK layout as well, and they're still in the EU. Of course, the letters and symbols printed are different from e.g. the Swedish layout, but the key locations should be the same.

Because it's what people are used to. From experience I know that switching between US and UK layouts is rather painful: the key sizes are different, some keys are in different locations. One downside of having a "special" layout than everyone else is that everyone else's computer is harder to use (and also, harder for others to use your computer).