It's not against the law to break into a house unless you intend to do something illegal.
That's absurd. The law is literally "Breaking and Entering" which would be broken as they did so with the intent to commit an offence. Your legal system would be a mess. "I didn't B&E, the window was left open!"
I'll give you some examples:
- enter a house for protection/shelter/aid or other emergency - not a crime
- enter a house you thought was abandoned to smoke weed - trespassing
- go into an understaffed hospital ward to gather supplies - B&E
The "break" is not literal.