Hi @rifatspir,
It can be difficult to support styling/exporting/maintenance of HTML in the editor. This is especially a problem for a page because there are styles that should be done via a CSS file and HTML in the editor could change at any time. There are also other items on a page (i.e. headers, footers, sidebars) that could be messed up if the HTML isn’t done well.
However, I view a custom product tab differently than I would view a page. A custom product tab is a single isolated piece of content and it shouldn’t be subject to the changes that a page would be.
If you know what you’re doing, adding HTML to a custom product tab is a perfectly fine solution.
Cheers,
Kevin.