Possibly you would prefer somewhere with formica topped tables / lino flooring and sauce bottles with encrusted sauce around the top ?
There's a very good reason why Gloucester Services was crowded. When Tebay opened, it set a new standard for motorway services, and, proved very successful and popular as a result. Gloucester has built, and developed, this reputation for quality hence it attracts customers who don't want to endure the usual dire services...although some are, marginally, better than others. Taunton Dean was usually avoided...any idea why ?
I should add, that, over the course of my life I've visited many service stations, for both work / leisure journeys, and spent a few overnight stays in them, hence I'm qualified to comment.
You mention the food. M&S, notoriously over priced, do have a varied range, as do Waitrose...however, one teensy difference. Their products are mass produced...those at Tebay and Gloucester are locally produced. I am more than happy to pay for the quality and variety at both.
I was unaware there was a dress code at motorway services....presumably you've never been on one late Saturday night / early hours of Sunday morning ?...eclectic would be the best way to describe the attire on display.
There again, normals, and the normal world, are alien to many on here, so no surprise you were shocked.
As for the dog, well on the surface, the lady shouldn't have put it on the counter, and it must have been a very small dog, but, if dogs are banned, and, thankfully, common sense prevails, how else is a single person, with a dog, expected to get served other than by having the dog accompany them to the servery ?