The lack of volume in eyelashes is usually a result of them thinning or falling out due to a number of potential factors.
Thin eyelashes are often associated with age. As we get older our hair follicles may slow down or stop producing eyelashes altogether, causing them to not have the same length and fullness they once did.
Thin eyelashes can also be a result of excessive eye rubbing. This can damage the skin permanently and cause eyelashes to fall out.
In other cases, the issue is caused by certain treatments and medication. A hormonal imbalance can lead to thin lashes, and immune issues can also cause problems with hair production. However, in most cases, the appearance of thin lashes is entirely hereditary and is passed down from the parents.