Because there's plenty of slang that doesn't inhibit use of the word by its earlier definition. Nobody blinks when you ask for a "box". Teenagers might giggle at Dick's stores, but it hasn't hurt business.
I don't think "box" is understood at all in the UK to mean what it does in US slang, though we do use the word in the context of cricket to mean something quite specific!
I agree that it doesn't inhibit its use as a product name though. Git seems to be doing just fine.
I'm Irish, not British, but the slangs are similar. "Bender" (on it's own) would mean a gay man. "on a bender" would mean a drunken thing. I'm not sure if people ever need a word for "thing that bends", since that rarely comes up. People might say "bendy bus" for an articulated bus.
As evidence, I give you Ofcom, the British state body which regulates things on TV & Radio. If you say offensive things on TV/Radio, they'll fine you. They did research in 2016 about offensive words[1][2] and have listed them and have advice. For "bender" they say class it as "Strong language, generally unacceptable. Seen as old-fashioned, but derogatory to gay men." [2]p10, and class it alongside: "dyke", "tranny", "homo", "lesbo", "muff diver", "he-she", "tranny", "carpet muncher" or "bum boy".
That should give you an idea of whether it's acceptable to use it now.
"Box" is not on that list, I don't know what that means. "Dick" is listed as "Strong language, generally unacceptable pre-watershed. Seen as vulgar and distasteful by many. Less problematic when used in a humorous context, and generally considered slightly milder than ‘cock’.", which is a similar classification to "bender", or "raghead", "negro", "kike", "slut", "cocksucker", etc
[1] https://www.ofcom.org.uk/__data/assets/pdf_file/0022/91624/O...
[2] https://www.ofcom.org.uk/__data/assets/pdf_file/0023/91625/O...
> to what degree?
Less and less.
a) homophobic slurs have become generally less acceptable
b) US cultural influence makes people more aware of multiple meanings
c) Futurama is also a thing that people here are aware exists / fans of