Thank for posting this; it's a cool topic!
When people compliment me for being able to draw, paint, fix my car, or remodel my house, they will sometimes tell me that I have a gift and that they wish they could do those things too.
That's a cool experience, isn't it?
The same has happened to me a few times, and I've always appreciated it when a friend of mine gives me positive feedback about some project I've recently completed.
Most of the time the impetus for me doing anything is related to:
(1) My needs, tastes, and interests requiring things that need to function in a certain way, look a certain way, or withstand greater than average use & abuse.
(2) I pay attention to everything, including the costs of precursor materials of all kinds - so when I get a few bids to see how much it will cost to pay someone to do something I need taken care of, I'm quickly able to sort out their labor, materials, and overhead - and get a quick read as to whether their pricing is fair or egregious.
(3) Once I figure out that what I want & need is simply not readily available, too expensive, or will be much of a hassle to obtain - then I start thinking about how to build it from scratch, or modify some existing components to give them new life and purpose as I need them to.
I will often tell them that they could do it too if they give it a try. I am surprised at the number of these people that respond in the negative.
Most of the people I've met who had a similar attitude as such attempted some DIY project that was way beyond their skill set, and that they did not have appropriate equipment to make the job easier to do, and with better end result. This is hardly irreversible, it just takes reading, practice, and if you are lucky working as an apprentice/helper for someone doing similar/related work.
They tell me that a person either has it or they don't, and they just don't have it. I am amazed by this.
I hear you, and I agree with your amazement at such statements.
Perhaps what they mean is
"some people have a knack for such work and can figure it out quicker than others?"
Negative thinking is the worst thing you can start any project with - it's simply a bad idea.
Be rational, be logical, be systematic, do things a step at a time, so if you do screw up, then you only have to re-do one component of the work.
It is necessary to FREE YOURSELF to the fact that YOU ARE GOING TO MESS UP.
I never would've been able to do any of the things I have if I at least didn't try.
No one builds anything perfectly from start to finish that I know of; it is very common to learn from the project as it goes on, and adjust plans for its finalization to optimize the end result along the way.
How many of you run into similar responses.
Yes, I have.
Are SPs just more optimistic in what they think they can accomplish and just do it?
In my opinion SP optimism does matter, however I think there is a lot more at play.
We're able to creatively re-purpose things to make them function differently than originally intended.
We're not afraid to mess up, we know it is not some judgment of our worth as a human being, we're just building a bookcase or some thing - no big deal!

Finally, I think SPs are a bit fearless, in that they are not averse to trying out things outside their "comfort zone."
We pull past experiences forward, and apply their principles to our current endeavors, in order to create what we need, with what we have to work with, in the time we have to make it happen.
That's the natural SP problem solving workflow as I see it; I use it, and I've seen many of my SP brothers and sisters use this method similarly.
We're focused on the end result, on what we have to work with, and making sure the final product meets or exceeds specifications - and thus the details along the way of how we do what part of the work, or what we use to do it, kind of get lost in the mix, because even though they matter, they are not showstoppers.
Are we just more practiced? Is it really just innate?
Maybe we're simply more inclined to try such things, and that leads to us becoming more practiced.
As far as what is innate to SPs vs. others I think there is a lot of variance amongst different people on that topic - and although it makes sense that we will seek to do what we are naturally good at doing, that doesn't guarantee that others don't have the same gifts - we might have similar capacities are our brothers and sisters of different archetypes, but a different proclivity as to which strengths we seem to implement more than others. Maybe we're just more interested in such things?
Either way, I love massive workday projects where all types of people get together to make a common cause happen.
Those are cool experiences, and I will have more of the min the coming year to use these skills/gifts for the greater good.
Have a great evening!
-Halla74