Is the Webmaster a Necessity?
Remember the days when computers were mysterious and only the truly technically trained folks could make websites work? Arcane markup languages were the way to make magic happen. Have you noticed how much things have changed?
Well, in a way they have not changed. A much wider variety of arcane languages make ever-more complex magic happen on websites. But parallel with this complexity has come an expectation that there will be a web-based interface that a reasonably non-technical person can use to control, manage, and update the content of the site.
Depending on what your website is built with and what it is designed to do, you may find that maintaining your site is amazingly easy these days. If you can compose and send an email successfully, you can probably maintain content on a site built in, for instance, WordPress or Magento.
Why? Because software meant to “hold” a website usually includes a management interface that makes it easier for a non-technical person to update content without damaging the truly geeky details (navigation, styling, actions).
All those geeky details are still there making the site appear and behave as you want it to, but you can edit and update your pages without knowing or writing XML or HTML or CSS or JavaScript or Java or PHP or anything else of that nature. If you DO want to get into the nitty-gritty programming details, of course you usually can – depending on what the website software makes available to you. But you don’t need to write code for most routine maintenance of many widely-used website programs.
For example, here are the editors for a Magento page and a WordPress page. You can “just type” and use common editing tools as you go. Things like adding bulleted lists or making something bold are push-a-button easy.

Magento lets you create pages in an embedded content management system.
WordPress lets you create pages in either an html or a WYSIWYG editor.
It may well be that you do want a webmaster so that you can pay attention to other aspects of your business while your webmaster maintains and develops the website. You may want a third party available to step in for non-routine changes when needed. That decision is a matter of choice, not necessity, for many folks. The software world keeps changing. Have you looked at your own website software lately? It may have become easier to use in more recent versions.