The first two are browsers; software, the second two are stores of knowledge.
Browsers have been free for the longest time now, they are a commodity; the 'for pay' browser market died a long time ago. Possibly that was a mistake but that's where we are now and the parties that supply browers (Mozilla, Apple, Microsoft, Google to name the bulk) all try to win marketshare because they benefit from having more users. Putting up a barrier will automatically play into the hands of the opponents.
Wikipedia is a free and much larger alternative to EB, which historically was very expensive. If Wikipedia goes away there is no longer any incentive for EB to have a free tier, which is the one thing they can do to erode support for Wikipedia a little bit.