"Boom" is also associated with the sound of an explosion. You don't want your planes associated with explosions. I think the mass market has a much stronger association boom=explosion than boom=sonic boom.
There is a huge difference between sounding like an advanced feminine product, which from your follow up post is what you're getting at with the iPad comment, and using BOOM in the name of a company in an industry that has lots of dramatic media coverage and footage of mid-air explosions, landing explosions, explosions just after take off, and so on.
All they need is a single incident, not even involving an actual explosion or deaths, and the brand will be irreversibly ruined forever. Why put your company branding on such a thin razorwire of acceptance in the first place?
> Boom's airliner is designed to maximize efficiency while producing a “boom” at least 30 times quieter than Concorde's.
Did you also predict the failure of the iPad in the marketplace, due to its unfortunate name?