Why are iOS files on my MBA hard drive?

An iPhone can be backed up to either the iCloud or to a computer. In order for the latter to happen, the phone would need to be physically connected to said computer. Regardless, the backup process would still require user intervention.

The end result of this would be what you are seeing on your Mac.

... so, at some point, the phone was "configured" to back up to your Mac. If this is not where you want the backups to go, you first need to verify that the phone is configured to send it backups to iCloud.

... and, yes, you can delete them from your Mac if you have no need for them.

Ref: Backup methods for iPhone, iPad, and iPod touch - Apple Support

Please note that the other possibility is that this is not a backup, but is an iOS update. These would be stored on your Mac if you did not do the typical "over-the-air" update, but again, connected your phone to your Mac to do so.

To add to Tesserax’s post, if you update iOS using your computer it will back up your phone to the computer before updating so you have a backup if the update fails. And the size of the iOS data means that it is a backup, and not an update; an update file would be only about 6 GB.

There are some differences between computer backups and iCloud backups→About backups in iCloud and iTunes - Apple Support

And, while not directly relevant to this discussion, once you connect your phone to your Mac and “trust” it you can enable backup and sync with the computer over Wi-Fi for subsequent backups and updates.