Why does this matter? They don't advertise so page views don't count for revenue. They're primarily kept up by a small group so they aren't missing contributors. They pretty much just have to dish out less bandwidth which means lower overhead and fewer fundraisers. Wikipedia having less traffic sounds like the best possible outcome for wikipedia.
It should. HTTP stands for Hypertext Transfer Protocol. It a series of rules that govern how information is moved on the internet. Every time you load a web page, information (hypertext) for the page is transfered from the server to you computer by these protocols. HTTPS is HTTP Secure, and when it is used, the information is encrypted. Bots do not do well with the encrypted information, and so their page views never happen. I get shakey here, and my Google-fu isn't helping, but I believe bots have difficulties with encrypted information because they operate similarly to the third-parties encryption protects against. So, this isn't a Wikipedia thing, but instead an internet wide thing.