Amazon Ads are not spending the budget

Hi,
I created new campaigns for some of my products and the budget is not being spent. For example, I have a budget of 10USD per day and I only spend 0.5 USD per day (some days 0 USD).
What does this mean? Are my bids lower than my competitors and that is why Amazon doesn’t even show it to the customers?
I believe that my presentation and product images etc. are good enough to generate clicks. I am trying to find the reason of this issue, so I can work on it.