Excel 2013 cannot open simple text file with .acc extension

You can easily replicate:
1. In Excel fill several cells with random information.
2. Save it in csv (MS DOS)
3. Try to open this file in Excel through Open dialog.

It's much more simpler just to rename file's extension to .txt or .csv and then open it. But it's not so simple when you have to rename hundreds of these per moth. Think of how many people are working with it too!

New MS Office decides to open .acc files differently while old MS Office handled it perfectly. No one knows why, no one knows what for. Typical MS behavior.