It sounds like you, or anyway the startup(s) you've known, have been fortunate. All I can say is: it doesn't always work out that way. NB that the scrutiny of the large player or the large player being at all involved isn't required -- only the potential acquirers need to know about the patent.
I believe that *some* small-company shareholders come out modestly pleased with what the patent system did for their pocketbooks, but there are others who come out quite displeased. And I suspect that in net, if you're involved in an early-stage startup and don't yet know how those dice will fall, your expected value from the patent system is negative.