annexations are mistaken a lot of times. annexations can be just as defensive a move as they can be offensive. gaining land will give you a little increase in income, but what can be very vital at most times is the manpower received. If france is pimp slapping you around for 20 years, your best way to end it is to "unite" with your neighbors to form one strong nation in defiance against french aggression. sometimes your neighbors are stupid (all the time when they are AI ) and you have to prove to them your play will work by showing off your mighty army. by the time you have completely annialated their army with yours and sieged their capital to the ground, they will be fully convinced of how much stronger you two can work together, under your leadership ofcourse.
by increasing restricts on annexing and BB points, you make it less viable for in-land countries (austria, brandenburg, venice) to ever be able to hold their own. The leaves all the power to france (powerful in and by itself) and the colonizing nations (spain, england) and also russia and the ottomans, who can grab vast amounts of land with only have to do a minimal of annexing.