Github doesn't even serve ads. What exactly are you worried about? Your throwaway email being primary key #78,000,000 and having your visited repositories stored in another table?
There's no good to come of requiring people to log in for the consumer. Online Tracking is never good for the consumer.
Most people have their real name and e-mail there because they use it to sign code in trusted repositories, so it's easy to combine these data with other sources.
> Affiliates: Personal Data may be shared with GitHub affiliates, including Microsoft, to facilitate customer service, marketing and advertising, order fulfillment, billing, technical support, and legal and compliance obligations. Our affiliates may only use the Personal Data in a manner consistent with this Privacy Statement.
The last time I tried, I'm pretty sure the email address was rejected right away, and the account couldn't be created.
Not being able to reasonably create an account there is certainly annoying when it comes to performing simple searches.
It has also prevented me from submitting new bug reports and adding information to existing bug reports for a number of open source projects over the years.
I'm always disappointed when I see an open source project using GitHub, because it makes contributing to that project more or less impossible.