It's essentially because of shitty parents allowing kids unsupervised access to the internet, rather than expecting parents to parent they pushed the cost/risk to companies.
Imgur decided they didn't want to foot the cost/risk and pulled out.
As a brit, I don't blame them, if I was US based I'd geoblock the UK as well.
Not least because it's the only way this will make enough of a stink for the gov to climb down.
Is that info from Imgur? Or from conjecture?