There's always more to be said; while we wait for that, u/WARitter has dealt with this subject previously. This thread asks basically the same question from another direction, and in this answer he expounds further on the difficulties armour had to face to be effective in a world of increasingly effective gunpowder.

And as it happens, the armies of the 1700s and 1800s did use armour - some heavy cavalry units called cuirassiers kept their armour throughout these periods. u/AncientHistory provides an overview of the effectiveness of cuirassier armour in this answer.