After testing it out over the past few months, Instagram is now rolling out the option to download publicly posted Reels to your camera roll, which will provide another way to share Reels content.
According to Instagram chief Adam Mosseri (on his Instagram channel):

"In the US, we're rolling out the ability to download reels shared by public accounts to your camera roll. Just tap the 'Share' icon on a reel you love and select 'Download'."

That will expand sharing of TikTok videos, which, even lacking a direct link back to the creators' profile, can still help to promote the branding of the creators via their username on the video.

Though there are some drawbacks. Some users have noticed audio problems with some of the Reels content, potentially due to Meta's licensing deals with music. We've requested more information on this feature from Instagram.

You can also choose to have downloads of your content disabled via Account Settings, so not every video will be downloadable, while you can't download content uploaded as private.

And only to select users in the US, for now at least. Otherwise, this adds yet another avenue to expand a content creator's audience reach, building on what has become familiar practice with TikTok, where one can download videos for years, basically forever.

That's as such, the only surprise about this feature is that it has taken IG so long to introduce this functionality; however, the firm would have probably been trying to ensure creator safety by making linkage possible back to the original post within the app. Or the firm was hesitant to permit download and reuse of an IG post elsewhere but in either case, here now so stop asking so many questions.