I agree - though I've not been particularly systematic, following one line or set of clues that seem interesting or fruitful, then moving to another as the fancy takes me. The cousins and relatives by marriage have brought all sorts of things to light, from missionaries in China to Boer War casualties, to anti-slavery patrols in the 19th century (and indeed in 1931) to slave owners in Jamaica and Texas, and all sorts of insight into 17th century village life. I've found settlers and pioneers from Nova Scotia to Chile, from Kenya to New Zealand; I've found all sorts of things.
But I'd agree that a family tree which only has dates of BMDs is not of compelling interest if you go back several generations, unless it can be set in context of the events of the time.