The behaviour is on purpose:
Create responsive tables by wrapping any .table in .table-responsive to make them scroll horizontally on small devices (under 768px). When viewing on anything larger than 768px wide, you will not see any difference in these tables.
Which means tables are responsive by default (are adjusting their size). But only if you wish to not break your table's lines and add scrollbar when there is not enough room use .table-responsive
class.
If you take a look at bootstrap's source you will notice there is media query that only activates on XS screen size and it sets text of table to white-space: nowrap
which causes it to not breaking.
TL;DR; Solution
Simply remove .table-responsive
element/class from your html code.