Why does Ebay prevent sellers from combined shipping with their Global Shipping Program?

[beancount15]

What would the logic behind preventing combined shipping with the Global Shipping Program?  What would be the incentive from buying multiple items from one seller?  It's such a waste!

[Anonymous]

I usually ask seller if they can combine and if they won't then don't bid or buy from those sellers.

As I always have said it is a conspiracy on eBay's part for getting more $$$ with GSP that way and also with the so-called import charges which I have never been dinged with the import charges weekly, so why the heck should I start to paying the so-called import charges by eBay.   It may be okay for very expensive items but not on small items like photos, DVDs, books, magazines, etc.

Other thing if sellers won't opt out of GSP, I always tell them "your loss and good luck".  Many of them told me that they lost many regular customers and also many potentinal buyers because of that. 

[pjcdn2005]

I haven't tried it but have been told that if you sign into .com and use the cart there, you will be able to combine items from the same seller even if they use gsp.  I'm not sure how the system  would then figure out tax and import fees but I suspect that if you combined two $10 U.S. purchases in one package then you would have to pay tax as the total would be more than $20 Cdn.