system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are anti-virus programs pretty big in size?
gpt
A lot of the older or more-established AV software are doing a lot of things.  They will have started out by doing anti-virus but over time they were competing with each other to add more features so that people will buy their product.  So now you get AV software with backup utilities, filters, website monitors, nanny software, etc.  Because they are doing a lot of things, they are now pretty big.

Related to this, tech-savvy users are preferring smaller AV software simply because they do one thing and none of the extra bells and whistles.

Larger companies tend to use the older more established, bloated AV software simply for peace of mind or force of habit or for the support, even if the features are not needed.  Because these older AV companies have the business of other companies, reducing their footprint is not an immediate concern.