It's more a matter of being messy rather than complicated. You're trying to track users who often visit your site multiple times before purchasing, coming from

It's more a matter of being messy rather than complicated. You're trying to track users who often visit your site multiple times before purchasing, coming from different sources, on different devices, and somehow tie that attribution to the purchase. None of the data inputs are consistent nor tied together. Analytics tells you differently than your ad platform, your payment processor tells you yet another thing, and your email marketing tool, and your CRM. (And if you want the serious tools for data monitoring and reporting have moved to focusing on enterprises...) You have to somehow factor in refunds, free trials, prorated billing, early cancellations. You have multiple ad campaigns running ad variations. Don't forget a/b testing. Finally you see some data point that hints something might be working, but you know you have to account for all the other factors involved. Did I make any website edits that day? Did the ad network change their algorithm slightly? Was there a holiday affecting traffic? When did I insert that new ad again? Wait, I know I changed my ad bid at some point... Did I get an influx of traffic from another source? Was it just a fluke? If you want good, real data, it's messy. And far from a solved problem.