I've very rarely experienced high-end places which add a gratuity for parties less than 6. I absolutely understand why restaurants do add a gratuity for larger parties and I do understand the places that do it for smaller parties in venues which cater to foreigners who may simply not know how to act in the US.

I don't think it's really a matter of preference. It's a matter of local custom. Part of travel is adopting to local custom, so it's just not a big deal.