English is not some objective, natural thing which exists outside of its usage by people. English is only how it's used by people.

I would wager that for the majority English speakers, the words "theft", "robbery", and (to a lesser degree) "burglary" or more or less fully interchangeable.

They may not be interchangeable in law, but the usage of English in law is famously not always in line with common usage, which is why we have "legalese" which many completely fluent and native English speakers may have trouble understanding without specialized legal training.

ESL here. To me, there is a very clear distinction between these terms, which also applies in my native language: A thiefs tries to steal without you noticing, a burglar is a thief that additionally enters a building, and a robber in contrast steals while intentionally confronting you. The intention and the level of danger each of these pose is quite different.