My company doesn't and a whole slew of ones I've talked to don't either... I'm not sure what bubble you are living in where you've "never heard of a tech company not do it'.
Microsoft has this program but it's pretty bad. Only masters courses are allowed with managers approval. Rest is out of pocket. Most managers don't approve. Tuition benefit is very much a myth.
Microsoft tuition assistance is available for both undergraduate and graduate programs. There are annual limits to how much is reimbursed and you get more for graduate school. Yes, it does require manager approval too. (I work at Microsoft)
