DBtruth is spot on. Whilst it is infuriating for those of us who have to use these spaces for the extra width (to bring a wheelchair alongside in our case) or because of walking difficulties, whether we agree with it or not the blue badge scheme has been opened up in recent years and people with mental health issues can now obtain them. Plus, of course, anyone who is elderly and has any form of mobility issue (as most do as they age). So there are far more people with blue badges now chasing the same number of spaces.
I tend to do as kezo does and ‘helpfully’ remind them that they’ve forgotten to display their badge, but it’s very high risk to be confrontational. We have simply forgotten to display our badge before and once we were in a motorway service station and a big pickup swung into the space next to us and a family of around 6 all piled out. I was about to say something and thankfully I clocked the accents and realised that they were gypsies. I suspect that if I’d said anything I would have regretted it!