Why do I only have double eyelids from certain angles? (Photos)

Although an in-person exam would be necessary to provide a definitive answer, based on the photo you have provided it does appear you would be a suitable candidate for upper blepharoplasty to create a defined and symmetric crease. During the surgery a small amount of fat will be removed, and your crease will be formed and set at a bit higher. If you want the best idea of what is possible for your eyes, do your due diligence, find an experienced surgeon, and have him/her evaluate you in person and discuss your options. #drdonyoo

It is not rare to notice this - I see patients with this concern. The anatomy of your eyelid skin, fat, and levator can change over time. A conservative DES (likely no fat removal and little to no skin removal) would yield a consistent double lid appearance and improve the heavy feeling over your eyes and lashes.