Hi,
thanks for your question.
The reason for this is that PHP code does not work in table cells by default. You can however enable PHP in table cells by installing a small “TablePress Extension” (see https://github.com/TobiasBg/TablePress-Extensions/blob/master/tablepress-php-in-tables/tablepress-php-in-tables.php ).
However, I’m not really sure that the approach of using TablePress for this a good one. Unless you really need an editable table, it might be easier to just use PHP (for example in a WordPress Page Template) to print the HTML code for a table, filled with your user data, to the page. You could then (if you want this) add the sorting/filter/pagination features, by manually loading the DataTables JavaScript library from http://www.datatables.net (which is the same JS library that TablePress uses for these features) into the page.
Regards,
Tobias