Why is there no "Partner Track" for software engineers?

Considering the hours worked, many software engineers earn as much per hour as a lot of lawyers. There are many highly skilled jobs in software, some requiring a three year masters degree or four year PhD. A JD only takes three years. Why then is there no "Partner Track" for software engineers?

Now most developers work for companies that are either in the business of selling software products, or using the software for internal business purposes. The lawyer equivalent is corporate counsel, and they don't make partner anyway, so that excludes most developers from the comparison. The law firm equivalent for software would be the custom dev shop/consulting firm, and there are still quite a lot of those, but instead of seeing programmers as partners they see them as easily replaceable contractors. Instead of valuing knowledge and expertise the trend has been in the opposite direction, to offshore as much as possible or use cheap H1B hires, and to hell with the code quality. Why?

Why are lawyers seen as such an integral part of a law firm that they share in a large part of the profits, while a software engineer working for a consulting firm is lucky to see a tiny bonus at the end of the year*? Why is it not common to see small to medium sized software consultancies that treat developers like partners? Is there just not enough profit in software development, or is there not a good way for a programmer to demonstrate his worth to a company like a lawyer can when he wins a big case?

*sometimes called "profit sharing", but usually such a small share that it's an insult to even call it that

** Even though founders can be partners, I'm not considering startups to be an accurate comparison because to get rich off that requires timing, luck, and usually being bought by a larger company. A lawyer doesn't have to get in on the ground floor to make partner at a firm.

** I'm also not considering corporate giants like the big 4, even though they can afford to pay well. Their annual revenue can be over $100 billion, while the largest law firms only have ~$2.5 billion.