In a blinkered environment, or if you want to be a programmer only - sure you can get away without knowing Office skills. But you will really benefit from them. I agree with Expressions, until you have started using it, you won't realise the power you can get.
Excel is used for all sorts of things - want to do infrastructure sizing for a system, you'll need a calculator and some regression capabilities, or some Erlang spreadsheets? Want to plot some gathered system performance metrics to show trends and highlight issues, and be able to pick and filter the data to plot? Want to quickly work out the total hours of work you have committed over the next week and how much of your time is spent on admin? Nobody believes you that 80% of the time is spent in a method call and is bottling up the system? Nothing speaks like a picture, and Excel can be used for all of this.
If you want to be considered for promotions, as a team lead, or as a serious professional, you'll need to be able to use these tools. They are used across most business and government organisations, and your ability to use them to communicate effectively will make a difference. And you won't be promoted unless your manager thinks you can already handle the skills - people generally aren't hired for roles that they have no skill in. These are business standard tools. One book per app, is all it will take ...
If you're going to learn office tools, and you should, I recommend you learn your spreadsheet tool first (Excel).