They're only weeds if you don't like them. I like to let them flower in our lawn along with all the daisies. Unfortunately Mrs A finds them not to her liking. I always leave a patch unmown to give us some colour and the birds and bees somewhere to play.
I have lots of this stuff in my garden, and absolutely encourage it!
It brings predatory insects into the garden, like hover flies which feed on pests such as aphids, I've also noted that goldfinches come in to eat the seeds they produce, and of course the bees that do so much pollinating.
So yes, I agree leave them for the birds and the bees