Why make ocarinas?
After going through the process of acquiring materials, and learning methods, there is nothing like hearing the first sound from an instrument you made with your own hands. Once you've made a few ocarinas and had your first success, you will likely be caught by the endless quest to develop the perfect instrument.
Enhanced playing comfort
Different people have different hand sizes, shapes and different degrees of muscle flexibility. Consequently, an ocarina which feels fantastic to someone else may give you an aching thumb. The placement of finger holes, and weight distribution, make a big difference to the playability of an ocarina.
If you make your own ocarinas, you can make them just for your own hands offering the best playing ergonomics for yourself. Leading to a more relaxed playing experience and fewer miscovered holes.
Making a few ocarinas is one of the best ways to increase your understanding of the instrument as an ocarina player. Doing so gives you a deeper appreciation, and insights into the instruments characteristics and limitations.
When you make your own ocarinas, you are not limited to creating them in traditional shapes or fingering systems. Unlike most wind instruments, ocarinas do not depend on the placement of finger holes for correct intonation. This allows great flexibility in both visual design and fingering systems.
For example, you could make an ocarina which natively plays a pentatonic scale, a minor key or a non-western tuning. You are also free to make ocarinas with any sculptural design you can think of, and glaze it or otherwise finish it any way you wish.