Why is UK passport control so much stricter than in the Schengen area?

Most other EU countries have land borders, and can't police them effectively, so they rely less on border controls and more on internal controls. The UK and Ireland have no land borders except with each other, so can realistically police all points of entry and then not need things like ID cards for internal controls.

This is my observation as well, though even within the Schengen Area it does vary depending on the airport and the nationality of the passenger being processed.

For example, at Zurich airport they almost always ask non-EU pax basic questions, sometimes more, and sometimes even ask me as an EU citizen where I'm flying from/to. Also, I've had my ID card examined with a UV light a few times. Usually, however, it just takes 10-15 seconds: quick glance, putting the card into the reader, swiftly checking the screen, and done!

At Memmingen airport, however, they only ever swiftly scan and stamp documents, including for non-EU passengers (Georgians, who needed visas at the time). They never even scan my ID

So it does vary, but they're indeed stricter in the UK, at least at the London airports, where they usually ask me why I'm coming to the UK and how long I'm staying for.

Most likely, it is as simple as the UK having (even) more problems with illegal immigration and being tougher on it. Furthermore, the lack of exit border control (save for occasional spot checks) makes it difficult to penalise overstayers unless they return (because of the electronic passenger record), which could be why they want to be extra careful not to let in the wrong people in the first place.