Sometimes people can see in through your window if they're standing in the correct position and they're looking in that direction.
I can actually look out my office window and when my neighbors window has the curtains open in their living room I can see right into the living room without any problem.
I'm not spying so don't really stare but I'm just looking out my own window and there living room window happens to be in sight of my office window.
Having blinds can help let light in but also stop people from viewing into your window so maybe get some window blinds if you don't have any yet.
Personally I don't care if someone sees into my office except for the fact that it could be someone who wants to break into my home and steal my computer and other office equipment I need for my home business.