We rescued our current dog in December - we'd lost our previous one in April last year. She was a staffy-mastiff we took from a small rescue after she'd been from one home and back again, etc. several times - she was traumatised by the regular 'be rehomed, form a bond, be rejected and sent back to kennels' experience she'd had.
It took several months for her to relax and bond with us and when she did, all she wanted was us - she'd be pefectly civil to other people, but wouldn't even wag her tail at them, so badly was her trust in other humans destroyed. She loved us to pieces, however and we felt the same about her. When she died, we grieved terribly.
New boy was 11 years old when we took him and we deliberately went out to get an older, male, black staffy, because they are the most overlooked. We adore him.
I say all this because it breaks my heart to see people paying money to breeders and then so casually discarding the dog when it doesn't turn out the way they expected. To do it once and learn a lesson is OK - but to repeat several times is appalling. As someone said, dogs form very deep emotional bonds with humans and they are damaged by being dumped.
Every day my phone turns up an ad on Pets4Homes (such are the cookies deposited on it, I suppose) for a staffy someone wants rid of. It upsets me dreadfully.