I'll take a stab at the "why not build a consultancy business"...
It's not scalable in any shape or form. Despite having aspirational goals early on, every consulting company falls into the trap of becoming a body-shop. It happens every. single. time. You begin to feel less satisfaction about your services and proposals to clients because you emphasize "our talent speaks for itself" and it's polarized by your clients desire to simply want to pay X for Y and don't care how, what, or who delivers it. Being a one-man shop means that right from the beginning your client's expectations are set on you being the right man for the job and they'll get Y because they're going to pay you X. At scale (I'm looking at you IBM, Accenture, etc) you end up fighting with cost center budgets, and spend more time trying to squeeze quality and scope within a set budget, or risk overspending budgets and end up looking like a bad services partner. Building a consultancy sounds awesome at first, looks awesome at first, and then it slowly burns you down.
Another way of saying this is that scaling a consulting business involves a peculiar set of challenges which may or may not be animating for people like Patrick. :)
I enjoyed the process of scaling Matasano; I only left because Erin and I were more engaged with the idea of making a dent in recruiting.
Things one does to scale consultancies:
* Refine a recruiting and hiring strategy to make it easier to staff larger number of projects.
* Build ramp-up processes to take new consultants and get them to "billable" status quicker.
* Play with service definitions and rate books, so that clients that need Patrick-level delivery can pay extra to get it, while clients that just need deterministic competent execution of tasks Patrick was good at 5 years ago can pay less to get someone without the name brand.
* Develop systems to cross-train consultants so that more people get an opportunity to (a) watch Patrick deliver a project, (b) deliver a similar project themselves, and (c) help bring other consultants up to speed.
Because revenue is so directly tied to performance and delivery in a consultancy, I think it's a pretty good lab for learning how to effectively manage people.
It's also true that a lot of them just turn into body shops.
Horizontal scaling in consulting seems to be what you're so put off by, but I think at most lower levels, vertical scaling is still very possible.
For me, at least for the forseeable future, I'm pretty solidly convinced that I can earn more money by studying and improving my tech skills than I could ever earn by taking a side-job that actually pays me dollars in my hand.
Maybe one can "max out" and just know enough to get their job done, but I'm not there yet -- I frequently find myself ditching other opportunities for making short-term cash in favor of learning something new. That's why I would favor "building" over running a less profitable software business.
It's not scalable in any shape or form. Despite having aspirational goals early on, every consulting company falls into the trap of becoming a body-shop. It happens every. single. time. You begin to feel less satisfaction about your services and proposals to clients because you emphasize "our talent speaks for itself" and it's polarized by your clients desire to simply want to pay X for Y and don't care how, what, or who delivers it. Being a one-man shop means that right from the beginning your client's expectations are set on you being the right man for the job and they'll get Y because they're going to pay you X. At scale (I'm looking at you IBM, Accenture, etc) you end up fighting with cost center budgets, and spend more time trying to squeeze quality and scope within a set budget, or risk overspending budgets and end up looking like a bad services partner. Building a consultancy sounds awesome at first, looks awesome at first, and then it slowly burns you down.