According some sources,
"A device running Ubuntu 14.04 LTS will only tell you there is a new Ubuntu update after the first point release goes live. In Xenial’s case that’s July."
How do I upgrade now, then? Is going to 15.10 the only solution?
EDIT: question and answer are still valid for 16.04 to 18.04, but note that at least in some versions the wait is not until the first point release goes live, but until some information files in ubuntu.org about current versions are updated, which happens usually some days after the point release but not always nor automatically.