[dogma1138]

IP infringement and theft are different things, infringement is often done in regards to IP that is in the open, if I hack and steal your trade secrets which are by definition secrets and not protected by a patent what is that then?

And in any case you are arguing about semantics, "theft" is also technically not a singular legal definition but an amalgamation of different civil and criminal legal statues.

In most jurisdictions intangible property also does fall under the broader definition of theft: https://en.wikipedia.org/wiki/Theft

[isostatic]

Theft in the UK (England and Wales) is covered by the theft act 1978 (and previous)

A key term is intent to deprive, hence most people nicking a car will be done for taking without consent - no need to prove an intent to permanently deprive.

Copyright infringement is a whole separate law and is clearly not theft as there's no intent to permanently deprive.