If profit is not the priority, there's a lot of things a company can do. To be honest, from our own experience of scaling up the company, the years between 0-10 employees were the most difficult ones. Now, 7 years later running an established company with a great reputation and 20 excellent team members leaves a lot of room for experiments and doing things like this.
Cynically, it's a recruitment expense -- there's a pretty good probability of getting a good hire from posting this widely.
It's not, to my mind, an actual corporate handbook -- it's missing boring important things like "here's our password and security policy, please remember we have people's super-personal health data in our apps, so it's really important". I guess that's probably in the company Wiki or similar.
To be honest, we're currently not really thinking of growing the company much. But you're right.
However, this whole thing started out as a Onboarding Handbook for new team members. Then however we thought it's also a great book to share with the world. So we decided to remove certain items and have those in the internal wiki only.
Definitely 37signals inspired us in many of the things we do. I'd say half of our team have read their books and regularly read their blog!
Recruitment and marketing are definitely a good side effect, but as @znq mentioned earlier, we built the guide in the first place for onboarding our own team members, then we thought sharing it publicly would benefit the community.
