Sadly I agree too - I have Cats, not Dogs, but I've seen the same thing happen with friends getting panicky & rehoming their Cats because babies on the way - makes me 
I was very ill when DD was small, but I never ever considered getting rid of my Cats, one of whom was epileptic & both elderly, so yes a burden, but so was DD when I was struggling as I was back then, but they were all MY burden & one that I happily bore, as thats what I'd signed up to when I took them on
Those 2 Cats have both now passed, & we now have 2 more, both CPL rescue Cats, & the older 1 of the 2 was a classic - lets get darling DCs a kitten for Xmas
- oh its grown & it has a mind of its own & isn't so cute any more so lets throw it away
- poor thing was a nervous wreck when she came to us, she cowered every time I raised my hand to stroke her, so had obviously been mistreated by the woman of her old home :( - thankfully she's much calmer & a happy little thing now :)
The younger is a kitten we adopted, his poor Mum was thrown out because she was pregnant, as if thats the Cats fault for having irresponsible owners who don't get her spayed
So I don't doubt it goes on with Dogs too, & I personally don't think theres ever a good excuse for not living up to your responsibilities when you take any pets on, its not like you were forced into having them is it