The overwhelming majority of coding work (at whatever level, top or bottom) is carried out 9-5 in offices.
Also "top developer" != "open source developer".
You require the same amount of in-office management.
Every time that management decided as you say, they got something else as delivery.
As a result, getting more effort out of an outsourcer may feel as annoying as getting your insurance company to approve your claim -- their entire company culture/process has evolved and/or been designed to prevent this.
By contrast, individual employees (remote or otherwise) might get lazy or burnt out or have personal problems or something, but few of them are actually Wally from Dilbert, using all their available effort to avoid having to make any effort
The outsourcee is always motivated to do the minimum work compared to an in-house team that can focus on quality and efficiency for the long term benefit.
Very true, the thing is, companies go for developers with tons of OSS code and conferences both as speakers and attendees for two reasons:
First is the fact that you become a known quantity, OSS code is code that you have produced and that any prospective employer can look at and see its "quality". It also solidifies you as more of a domain expert which in turn allows you to get better wages.
Second, having employees with OSS contributions and speaking at conferences is good for the bottom line of employers, they can "gloat" more easily on how they have the "top talent" and are thought leaders of industry. This in turn allows them to charge their clients more and lets the find prospects easier.
It's all about perception and influence.
*Ninja Edited for grammar.