What's the advantage of creating gift links for trades instead of using activation keys?

Is this not enough of a reason to prefer links?
I don't know about you but for me and most of the traders,if not all, the main concern is safety and profit of course.

I guess it is a good reason. So you just visit the link right before giving it in the trade?

Links are easy to brute force and get stolen, if you plan on using them just don't generate them in advance.

You can verify the link is still good and if it is from an old bundle it is highly unlikely to be revoked from credit card or other fraud.

It is also handy for this site as you can see how redeems the game which just makes it easier to verify if they actually redeemed it to there account .I also like it to keep track if i have used it or not as sometimes i forget about bundle left overs and and with just a key and no way to mark it as used sometimes it can be a guessing game.

I also think it just easier dealing with the links as you do not have to be logged into steam to redeem them,you can just sign into the website.

Anyhow those are the pros i like a about them and i do prefer the only links myself.

for Humble links, won't the receiver also get OSTs, DRM free download link, and other bonus content as well (if any is available of these are available)?

I like to give humble links in case people want the item added to their humble library for whatever reason. But I never generate the links until I'm ready to give it out.

HB gift links also give the person you traded with a chance to get the key link and gift it to somebody else, which can be useful.

Gift links force to enter your e-mail or register on site (Humble Bundle, I dont know how other bundle sites works), so, if you never heard about them or didnt visit their site/ buy smth on their site/etc, you'll be like a new user (POTENTIAL CUSTOMER) after activating gift link. Keys dont allow to advert "mother source" of the free game. Something like this and IMHO :)