It goes much deeper than just coffee shops and other public wifi. There are people in oppressive countries that have to use VPNs to get around their country-wide bans of certain sites, such as anything that provides access to information. Reddit used to be a sanction for tons of information sharing. But now, with Reddit going public, they have to appeal to their shareholders, who probably have business or other deals in those oppressive countries. So, even if Reddit is simply trying to force users to be trackable, it still behooves the shareholders to make information and knowledge more difficult to access to certain people.
“Lockup” is an investment term. When a company has an IPO (Initial Public Offering, which is the day they become publically available for stock trades), the big shareholders and company employees who are invested ahead of the IPO are “locked” from selling their shares for a certain number of days. This isn’t required, but most companies having an IPO end up having a lockup period set as well.
In regards to this headline, it just means that the initial investors and big shareholders are now free to sell their shares, which they are apparently doing in droves!