- Because their products are made to work with their infrastructure, their frameworks, their internal systems. Just making the software for Google Wave run on some independent server would be a big job.
- Selling the software without the team that maintains it is a bad deal. It’s really hard to just read a huge pile of code and figure out how to work with it. When Google acquires a product, they usually acquire the team also.
- Who would buy a product that Google has decided isn’t worth it? New Google products launch with lots of free promotion from Google, including integration into their other products. If Google can’t make it work even with all that, how can someone smaller hope to make it work independently?