Can you get washing machine conectors without a valve built in? I
was really thinking of taps etc...

In any case, the same point still stands. You may wish to isolate one outlet
until the opportunity arises to complete a repair. If you have a badly
leaking tap that requires a 'O' ring to be ordered in, would you want the
entire kitchen isolated until you can get round to ordering and fitting it?

As isolating valves cost 49p at screwfix and take seconds to fix, why not
bother installing them?

Christian.