Squarespace is the easiest and most simple platform for small businesses to manage on their own. If your Squaespace web designer was to die or retire, you'd still be in the best position possible compared to other platforms (like WordPress and Shopify) to edit the website yourself or find someone else who can easily help.
That's because Squarespace is a closed-source web platform, unlike WordPress which is open-source. Open source means there is a lot of custom functionality that can be added, but that it is very code-heavy and requires a skilled web developer to keep up and manage to make sure it is still working.
But when you pay for web hosting with Squarespace, you're paying for their technology, which is very high quality and rarely ever breaks. If something on Squarespace isn't working, the team at Squarespace has hundreds of employees working to rapidly fix the problem.
If you are a small business, sole proprietor, or even a mid-sized business, Squarespace is the best platform to put you - the Client and business owner - in control of your website, and not in the hands of a web developer.