I don't think yabu to be upset. It's crap you didn't get a present.
But. You clearly knew (even without it being a fully formed thought perhaps?) that they wouldn't get exH anything if you hadn't taken them - or you wouldn't have taken them. Did you also pay for his gifts?
So it follows that if you didn't expect them to independently get him gifts, then you can't expect anything different for you.
And you know where you stand now with ex in terms of this sort of stuff. It could have gone either way, it's just unfortunate that you were misaligned in expectations this time.
However. At their ages it's not at all U to expect them to show some thought and initiative. It sounds like they've never had to, so not entirely their fault, but it wouldn't hurt at all to let them know they need to be a bit more switched on about this sort of stuff. Tbh, even if you were still together they're getting to the ages where they should be being more independent, a 14 Yr old should surely have the ability and awareness to enjoy the process of choosing a gift and giving a surprise to make someone happy. Even my 3 Yr old enjoyed handing out presents on Xmas day! (despite announcing she wanted all the presents
)
Are they generally thoughtless in a 'mum'll do it' way OP? I know I was as a teen, and lots are, but it may be this is a symptom of a larger attitude issue that's more noticeable and unsustainable now that your circs have changed.