Since users don’t touch the actual spreadsheet, there is no danger of exposing or unauthorized or accidental editing of the logic.
2) Version control
Your web app talks to a specific master version of the spreadsheet which cannot be altered by the general user, only by the administrators authorized to update the native spreadsheet. Version control becomes a non-issue. Furthermore, when updates are made, they can be rolled out instantly to your entire network of users.
3) Greatly enhanced accessibility
Since it is now browser based, anyone authorized to access the URL on your network can access the app. Finer access control is enabled by EASA, and an admin user can specify which users and user-groups can use which apps, and who can share (or not share) results and output. But even higher granularity is possible, for example only exposing certain parts of a spreadsheet do different user-audiences.
The interface you create (the web app) is no longer constrained to look like a spreadsheet (unless you want it to). Highly dynamic and fit-for-purpose customization can make your existing spreadsheets far easier and intuitive to use, especially for those not familiar with it.
Excel spreadsheets are often part of a greater process or workflow, and may involve any number of other software assets, for example databases, ERP systems, and CAE software just to name a few. EASA automates and web-enables complete workflows – for example, from Salesforce to a pricing spreadsheet to a PDF, signature-ready proposal.
A local version of Excel is no longer needed for the users, whether they are using a computer, an iPad or a smart phone. Besides the obvious benefit of enhanced access, you will no longer suffer from failures due to mismatches in settings, release numbers, service packs, etc.