Why? It's easy and quick to code complicated things these days. It's nice having custom dashboards and functionality that fits exactly with what you need. Way more professional.

I'm sure Google Sheets are fine. But I've been seen truly ugly Google Sheets with way too many tabs and horizontal scrolling. Clunky cells that seem to expand and have their own scrolling universe with different laws to everything else. Why can't I simply click the cell to copy it all, nope, let's try double-clicking the cell, I just want to grab the contents to the clipboard, nope. Now it expands and I'm scrolling the whole sheet and have lost my place because Google Sheets tries to snap to rows or something. Damn I hate this memory of navigating someone's horrible Google sheet.