Why do eBay sellers do this?

[mcs1056]

I sell on Ebay, mostly model kits. When I print the shipping label, I message the buyer with the tracking number (even though they get it through Ebay) and let them know when I'll be dropping the package at the Post Office. This is, in vast majority, the next day, unless the PO is closed for some reason. 

Last week I sold some newspaper print plates (Detroit's Tiger Stadium last game pages) to someone. I had listed them separately, but I was able to combine them in one package. So, I refunded the second shipping cost. 

Communication is key. 

My issue with Ebay is their fees. I list stuff there, but also on Craigslist and Marketplace. More local folks might see an item, and local pickup can be free. I get the same selling price without those fees. They save shipping charges. Win - win.