A spreadsheet is a reasonable home for your network. You control the rows, columns, and tabs, and can keep names and notes in a structure that makes sense to you. For a small network you are happy to manage by hand, that flexibility can be all you need.
As the network grows, you still have to scan the sheet to decide who matters now. Then you find the notes, rebuild the context, and write. Tenora puts your meaningful network in one orbit and opens to a ranked queue. The context and next step are together, so you can start with the reach-out instead of another pass through the rows.
TLDR
Use a spreadsheet if a flexible list and manual follow-up work for you.
Use Tenora if your network is growing and you want the next reach-out ranked with its context ready.