I didn't get that sense either, from the OP or Terry, rather, it's just that most ideas have been done when it comes to this stuff, so the odds are, someone has done it. That would go for your idea too, it's just such a small market with so little at stake that it's literally not worth spending the time a prior art search would require. I suspect 'borrowing' is more that there is just this pool of stuff people have done, and at some point, something almost everyone comes up with borrows from that pool of collective knowledge, like, oh, making something out of cuben or silnylon, for example.
In a sense this would be agreeing with you, given the relatively dismal state of the patent office and what they grant, if you can get a patent on something before someone else does, and if the market is small enough so that nobody else really exerts much energy to demonstrate it invalid, you're right, it really is your patent, and it would be a relative headache with relatively few rewards to try to get rid of it. So that does work. One of the more famous cases of patenting something so obvious nobody ever thought it worthwhile is amazon's 'one click purchase' patent, which I believe is still holding up. That is similar literally to patenting the use of silnylon in outdoor gear.
Personally I doubt your own business success has much to do with the patent, I suspect it's just a nice idea that's nicely done, like most cottage gear is, and the market is so small, as your numbers show, that it's not really worth trying to compete there, and certainly not worth trying to get into some patent thing that will never repay the legal and research costs. And there does seem to be a certain ethical standard among most myog cottage types, ie, in general they try to do their own things largely, give or take. And if you get sick of doing it, you might be able to sell the patent to some other company for some amount at some point, at which point you'd probably discover the actual value of the patent. Probably not a good idea to depend on that for retirement I'd guess...
Jardine's case was interesting, I have a climber friend, used to be world class in his younger days, that certainly grants the high value of the Climber's Friend device, that was unique and did change climbing, but he laughs at the notion of unique backpacking gear that is patentable, observing, largely correctly, that it really has been done before in almost all cases, but that shouldn't stop someone from trying to patent some idea I suppose, though personally I dislike such patent activity, but it is something one can do in the modern day USA if one is so inclined, ie, it's a loophole that can be exploited.
Jardine's later complaints though, those are just silly, his entire point was to make simple light gear that was easy to sew and easy to deal with, and to free you from corporate type outdoor equipment clutter and waste, and thus be, almost by definition, generic, I read his book a while ago, can't remember which one, an earlier one, and it was all about simple and obvious ideas that anyone could do. A tarp, a quilt, a bag style backpack? Give me a break. He just got older and needed to find a way to fund his lifestyle, that's all, and he'd sold his actually unique ideas long ago, and burned the golite bridge, which I'm sure happened for good reasons.