Very inconsiderate and rude and obnoxious and arrogant and entitled.
And I am sick of people making excuses like they have problems with misjudging time or 'anxiety.'
Do they also have these 'issues' when they have to catch a train, or a plane for a holiday abroad, or if they have an appointment that they have had to wait several months for (like a hospital consultation or dental appointment?)
You can bet your bottom dollar they don't.
Same question when it comes to cinema times, theatre shows, and job interviews. I bet they manage to get to THEM on time.
It is thoughtless and self-centred, and as has been said, shows that this person values their time more than you, and thinks their time is more important than yours.
I don't buy this 'they have issues' or 'they have anxiety' line, because, as I said, they are on time when it suits them.
I have binned off everyone who has treated me like this after the first 4 or 5 times they have done it.
Funnily enough, they don't like it when you do it to them.
One couple me and DH used to know (and decided to ghost a year or so ago,) were ALWAYS late when we arranged to meet them at the pub; like half an hour to an HOUR late. Always a fucking excuse! EVERY. TIME. 
So this one time (after this happening 5 or 6 times in 3 months,) we arranged to meet them at 7.45pm, and made a point of not even leaving the house til 8pm, so we wouldn't be there til 8.20pm or so.
At 8.10pm, they PHONED us, (well SHE did,) and asked us (in a shirty tone) where we were, as they were waiting for us at the pub and had been there FIVE MINUTES (So they had still been 25 minutes late!) 
Un-fucking-believable!
As I said, arrogant and rude and entitled.