One of the core differences between Microsoft and local accounts is that the former is a cloud-based account while the latter unique to the machine it is created on.The site says there have been reports about Microsoft hiding local account creation since Windows 10 version 1809. At the moment, it's not known whether this is a permanent change or a change that's still in testing phase.
A Microsoft Account offers certain advantages such as the ability to use it on multiple machines, access to certain tools and services that require a Microsoft Account, or easier password reset options. The main advantage of a local account is that it is more private and that it cannot be attacked that easily as local access is required to do so.
As an added bonus, the username folder reflects the full chosen username and not just the first five letters of the email address used to create the Microsoft Account.
If you do not want to use a Microsoft Account, you will need to disable your Internet connection during the installation. When the operating system doesn't detect an Internet connection it will offer the option to create a local account.