Why doesn't one of the UK's biggest mobile phone companies have an SSL certificate on their website?

I am so confused. three.com is one of the biggest mobile companies in the UK. I use them and they deliver great service. What's so weird though is that they don't have an SSL certificate.. why don't they just purchase one? I literally got mine for a few pounds, their company makes millions.

Their other website three.co.uk also doesn't have an SSL certificate. I'd really appreciate some answers

certificate cybersecurity mobile phone ssl uk