As user2723984 notes, academics often scramble their email addresses ostensibly to prevent web crawlers from harvesting their email address and spamming them. But it still allows humans to obtain their email address.
The effectiveness of this is debated.
While it is true that more sophisticated web crawlers could circumvent much of this, most are not sophisticated. Thus it does help protect against generic spam (but that stuff is mostly caught by spam filters anyway).
However, most academics continue to receive plenty of academic spam. This is because academic spammers harvest email addresses from papers via repositories like arxiv, where people do not use any kind of protection. (I know this because I receive academic spam at email addresses that only are in my papers.)
At this point, I think it is more of a piece of academic culture than a well-motivated practice. At least in computer science, most people do it. This encourages others to copy the practice and so it carries on. Some people go a bit further, e.g., "firstinitial dot lastname at thisuniversity dot edu", where you must fill in the name of the university as well as their name. (I personally find these riddles annoying. I put my email in an image on my website, but with the usual riddle as alt-text for blind people.)