It really doesn't, people just think it does :)

There is a persistent misreading of the law, mostly by engineers.

It's actually pretty close to most other states laws in practice.

If you work for a very very very focused startup, sure, you may end up owning some personal stuff. You would in a lot of other states too.

If you work for any mid-sized tech company or larger, you probably won't own much, unless your interests are really off the wall.

The law allows employers to claim inventions that relate to an employers business, which for most mid-sized or larger tech companies, covers a lot (IE Apple's business is not just phones and computers, it's mapping, video editing, music software, word processing, distributed cloud services, etc).

In addition, if your invention relates to any actual or "demonstrably anticipated research", that would be covered too.

So if's demonstrable that apple was going to start exploring (not producing) social games, any social games you made (direct), or social platforms (they are "related"), or heck probably even social apps ('related' to that research) or ... would also be arguably be covered.

Over time, the research of most tech companies quickly expands to cover almost everything (since they frequently seek new markets), even if they never do it, ....