Object-level security was introduced in the launch of Tabular 2017. This feature allows you to hide tables and columns from the end user.
The ability to hide columns and tables is vital if you need to do something like allow a salesperson to see their total sales, but hide the cost of the sale, which would also exist in the sales fact. Another critical example would be to restrict access to tables or columns that contain PII to managers or HR. In fact, I do not know how you can make a Tabular model GDPR or CCPA compliant without this feature, unless you exclude all PII entirely.
There are hacky workarounds to get a similar effect with row-based security, but they only work with simple, small models. I think anyone who's building a serious enterprise solution with stringent compliance requirements is going to really want this feature.