Wrong counts, no history, several people editing the same file: when a stock spreadsheet gets there, a system built around how you receive, move and sell stock can take over.
A spreadsheet often works well for a few dozen products. As the range grows, counts drift, rows get overwritten and it gets hard to tell what sold when. Workarounds help for a while, but each one is another thing to keep in sync.
If a packaged stock app handles how you sell, start with it: it will be quicker and cheaper. Custom makes sense when your business has something the app handles badly, such as bundles, consignment stock or unusual units, or when stock needs to connect with your own billing and LINE.
