Some degrees are just 4 years in length because there are 4 years of content (e.g. physio, podiatry), with some taking up to 5-6 years (BDS, MBBS)
In the US there is some distinction between 3 and 4 year degrees, but I’m not sure why, since undergrad for them tends to be a general studies degree (BA and BSc).
There’s this thing called the Bologna accord which aims to standardise the nature of degrees around the world - here, 3 year degrees are standard at a bachelor level, so it could be said that a 3 year degree is the‘norm’.