IAaIPL with a pretty big lawfirm, so I'll take a crack at this:
Why allow software to be patented instead of copyrighted?
There is no "instead." Currently you can obtain both: one for "original work of authorship fixed in a tangible medium of expression" (i.e., copyright), and one for the "new, useful, non-obvious" "process, machine, manufacture, or composition of matter, or any new and useful improvement thereof" (i.e., patent).
Patents should be for THINGS (concrete stuff).
Well, I'm sure that one make the concrete industry happy, but I don't think it is a logical policy distinction.
Snark aside, there are a few easily articulated reasons. First, it really depends on what you mean by "concrete stuff" and "things." There are lots of "things" that aren't concrete (we usually say "tangible"). But interpreting what you mean by "concrete" from your subsequent bullet, I'll tell you that your conception of the dichotomy between patents and copyrights is almost 100% inverted. Patents are essentially stakes in the ground around an idea whereas copyright is the protection of the actual expression of an idea. As it relates to software, it's the difference between the idea for the code and the code itself.
Second, the statutory classes include non-concrete things such as processes. This is the "because the law says so" argument.
Third, it's not just tangible things because it's very difficult to draw the line between "concrete stuff" and the not-so-concrete stuff. If you look at the claims at issue in this case, they're not just the algorithm. It's a computer programmed to do the algorithm.
Think about it like this: a lever and a fulcrum are essentially the mechanical expression of using a physics equation for leverage. If you were the first person to think of how to apply the leverage equation to lift things, that would be quite an advance--I have assumed away the obviousness issues since the inventor is the first person to ever think of it and focused only on whether it would be patentable at all.
Copyright should cover TEXT (abstract stuff).
It's not the "abstract stuff" that is covered at all. It is the actual expression of the abstract stuff that is covered. You do not get a copyright for your incorrect ideas about intellectual property, only the expression of it.
Seems to me that these systems should exist to prevent others from stealing your specific work, the result of *your* labor; not to prevent others from engaging in the same line of business. Which seems to be the point of much of software patenting.
If you've ever been involved in a copyright dispute, you'd recognize how little protection that actually offers you. Furthermore, if you've ever been involved in a major software development project, the amount of time actually writing a specific piece of code is diminishingly small compared to the other time, effort and energy expended to get to that point: design, plan, etc.
Viewed in this lens, protecting only the expression is not a lot of protection since it's easy to copy the idea without copying the code.
i have tons of doodles and outlines for things i'd like to see on the market or share.
Your individual experience says little about whether patenting and copyrighting advances or encourages innovation. Patents and copyrights offer some additional incentives. Those incentives are not enough for you, clearly. You are not along, there is a whole world of trade secrets for innovations that would be under-rewarded via patents and copyrights.
But your argument is really a push for MORE benefits; not less. You would be unmotivated to contribute to innovation under the current system. The absence of that system would not provide MORE innovation from you.