I see what you're saying. At this time, there isn't an option to completely delete inventory items but you can make the items inactive instead. Here's how: 

1.  Click on the Gear icon at the top right hand corner
2. Select Products & Services
3.  Select the products you wish to delete by ticking the check box to the left of their names. Alternatively, you may select all by clicking on the check box to the left of the Name header.
4.  After selecting the items to delete, click on Batch Actions at the top right and select Make Inactive

Give this a try and let me know if you need help.