It doesn't have to be a megacorp. Looping new people into a deep problem takes time, and can kill momentum if not done in a strategic way. Your personal time on any problem is finite, and you can exhaust that time-budget on bringing the wrong people up to speed. This is doubly true when the other person isn't on your team or in your organization: e.g., bringing in vendor support. (Maybe your experience is different; in mine, bringing in remote experts doesn't guarantee a faster resolution.)