Tiles Grout problem

The number one we face in our tiles is when grout start deteriorating.  Now I understand why my friend prefers not to put spaces between tiles in his floor.  In due time grout can easily remove through time.  Chairs can be the number one reason why grout become weak, leaving spaces between tiles.  In a situation like this we have no choice but to regrout the tiles to make it look good again.   But in my friend's house he doesn't have to worry about it because no grout can be seen in his floor.  I would follow my friend style next time when planning to have a tile floor.