It's impossible to say whether you personally getting a PhD will help you personally as an entrepreneur, but I'll give you some anecdotal insight into the level of educational attainment typical of Silicon Valley startups.
I'm unaware of any research of the success rate of startups and associated founder educational attainment. So - I expect anecdotal evidence is the best we can do.
I have worked in 5 Silicon Valley startups, and am familiar with many more from tiny two person shops to billion dollar unicorns.
In Silicon Valley, it is unusual for startup founders and early employees to have PhDs.
Of the 5 startups I have personally been involved with around 1 in 10 founders has had a PhD. Of those 5 companies, 1 grew directly out of academic research, 1 had some relation to academic research, and the other 3 had nothing to do with academic research.
I would estimate the percentage of early employees in startups I am familiar with having a PhD at 5-10%.
You can get a feel for this by looking at lists the startups funded by a various VCs, and then looking on LinkedIn to see the educational attainment of their founders:
Here is Andreessen Horowitz's portfolio of startups:
Let's take a look at a few of their companies and founders highest educational attainment:
- Actifio - MS
- Airbnb - BS, BFA, BFA
- Asana - Both founders are somewhat unclear, either no degree or a BS/A
- Box - No degree, BS
- Buzzfeed - No degree