I think one reason for that is British institution of a Chip Shop- also known as a "Chippy". This is a place that sells the classic fish and chips. And by chips they mean fries.
There are a few chains, but they seem to be largely independently run. They range from sketchy-as-all-get-out to fairly posh. I do have to admit that I've never actually been to one... I've been to a place called Metro (mixed reviews!), but it's a bit more restaurant than chippy. Ross doesn't really do fast food, so my exposure has been limited. (This guy is good for me in lots of ways!)
Then, it's my impression, that this lead to the general "take away" style restaurant that is prevalent here. Some of them still qualify as chippies because they do serve fish and chips, but they also serve... well, every other kind of fast food imaginable... seriously, burgers, pizza, even Chinese food... Yep. All from the same "restaurant".
So there are all these Chip Shops filling the gap that, in America, is filled by Wendy's, Whataburger, Taco Bell, Sonic, etc. Anyway, that's my theory.
I now leave you with a song that plays on the radio from time to time. It's got a fun rockabilly feel and it makes me smile. It hope you do to.
It was apparently released (in a limited fashion) to DJs in America with the lyric changed to ...works down the truck stop, but never got much notice... It was Kirsty MacColl's first hit in the UK in 1981, going all the way to #14.