The argument would be no different from all the products out there who design their own UI (MUX, GitHub). Our framework Frappé (and product ERPNext) has a great emphasis on minimal style, and we really wished the charts to be free of visual clutter (not have too many measure markings for instance). Something that even the customizing API should take care off. Chartjs is awesome and very comprehensive, it just didn't go too well with our look and feel :)
chart.js isn't perfect, but it's pretty easy to customise and remove/change any element you don't like. I find it hard to believe it was easier for you to create an entirely new charting library than to set the option to remove ticks.
I'm not complaining because it's always good to have options and I really like the look of your library. I just find it a very curious use of resources.
Of course, it's your business and you can do whatever you like with it regardless of whether you have a good reason. :-)
