Castling does two jobs in one move: it tucks your king away from the center, where most of the fighting (and most checks and attacks) happens, and it connects your rooks so they can support each other.
A king still stuck in the center on move 10 or later is a standing invitation for your opponent to open the position and attack it. As a rule of thumb, aim to castle within your first six to eight moves whenever the position allows it.
8
7
6
5
4
3
2
a1
b
c
d
e
f
g
h
Both sides have developed a knight and bishop. Both kings can still castle.
With development this far along, what should White prioritize?
8
7
6
5
4
3
2
a1
b
c
d
e
f
g
h