I became a trailer boater 48 years ago. At the time I didn't know squat about a trailer, so I went to the Libary (remember those) and got a book about trailer boating (remember books?). The book said unplug. So I did....and continue to.
My family boat trailer is 32 years old and has the original bulbs.
Maybe plugging / not unplugging it just lazy. I dunno. But to say you concentrate on the drain plug made me just choke on my beer. The tie downs, motor deflopperizer and drain plugs are trailer boating 101, learned on the first page.
The reason I have to wait so long at the ramp, watching neophites botch their launch, is because they never read the "book".