it may be because of two Reasons:
01. Audience Targeting: If you have very small targeted audience, it will limit the number of users who will see your ads that results into a low spending. Also, using overly specialized targeting options like location interest and behaviors will further impede on the performance of the ads.
Thus I Suggest: You can include larger segment of target audience who may have interest in the similar products/service as yours.
02. The Bidding strategy. If you are working on cost-per-click (CPC) basis; ensure that you offer a bet which is considerably higher than that of other bidders to win auctions and display your ads. And double check whether you are allocating your daily budget efficiently among ad sets and campaigns.
Thus I Suggest: CPM bidding would enable you reach out more people while spending less if at all you want to gain more awareness about a brand.
When these things are adjusted, campaign performance can be improved and the money will always be spent in daily budget for better results.
Do not hesitate to ask if you have any Questions!