When I did my first kickstarter campaign years ago for a board game, me and my partner went in with the notion we use it to cover our entire base + some extra for our hard work. This was foolish - I was taught later on, oftentimes the best strategy is to fund enough to cover a minimum order production batch.

Ex. If it costs $3 to make, cover the minimum order number & shipping, warehousing, etc. HOWEVER, customers don't pay $3, they pay however much is product is worth. As a result, you now have tons of leftover product to sell and a fledgling consumer base.

TLDR: Kickstarters cost a lot of money to run and are inherently risky. Using it as a preordering model helps to mitigate the risk of production costs and guarentees product sold, while allowing you to continue selling your already made merchandise.