Screen Adhesive in replacement kit

Hi, I ordered 4 new batteries to go in my family members’ iPhones. For 2 of them I purchased the extra toolkit. I thought it would be good to have one toolkit to perform the work, and then a spare one just in case. For the third and fourth phone, I just wanted the battery, “no need to end up with countless screwdrivers and other stuff I thought”, no matter how useful they are.

When wanting to perform the repair, I noticed my mistake: no replacement “screen adhesive”. So I went online to check, and discovered I hadn’t payed attention: the screen adhesive is part of the optional tool kit, not of the parts.

This confuses me: I think it’s always best to have a new screen adhesive after having opened the iPhone. Why is it not in the “parts”. Surely this is not a “tool”. Similaryly, the battery adhesive is also in the “parts”. And even if it’s not a direct part for a replacement battery, you need one to perform the procedure. (there’s a reason why it is available in one of the purchasing options - namely the toolkit).

I checked if I should have purchased the screen adhesive separately then, for a small additional fee. But to my surprise I found that while you can buy them separately, it costs the same as when you get them inside the complete toolkit. And it’s not that you get the tools free with the adhesive. These adhesives cost next to nothing in bulk.

Surely this is either a poor kit combination, or a lucrative way of combining parts to make the most money out of them? What am I missing? And am I the only one wondering about this issue? How about adding the option to add the screen adhesive to the battery part kit itself, without having to add the toolkit (screwdrivers etc), and make it less pricy. Or offer the possibility to purchase a pack of 5 screen adhesives for that price, making it a correct price?

Any thoughts?

Thanks, Stef