Why to use handmade vintage style Eye dropper fountain pens?

I got these vintage style eye dropper fountain pens after a long time from Indian Subcontinent. I love their beautiful color. There are bright and colorful. They have a small window at the barrel which are not very clear as they all are handmade fountain pens.
The nib is great and writes a medium as per Western Standards.

Why to use Eye dropper fountain pens?

1) The eye dropper system is a vintage system which was the base of the writing instrument and this is how the fountain pens were born

2) This filling system can use lot of ink with great ink flow

3) A very Eco-friendly pen, as no need to use the cartridges and converters and make the waste debris.

I have some pens on sale on ebay. Please have a look over it Exotic Vintage style Fountain pen