Same here for the wifi. I don't shop with my K3 wifi, but use if for file transfer. I only sideload books that are too large to send via email. I think that's only happened once thus far.
I shop for ebooks on my computer. Books I get from Amazon I just send directly to the K3. Books I get from any other store or the library are imported to Calibre and then in one step are converted to mobi and emailed to my K3.
Could I get by without wifi? Sure I could. I could also get by without an EBR too. But I find wifi to be incredibly convenient. And I love the convenience of an EBR.