Why use a hexadecimal number system?

Good afternoon, flipping through the github, and I see that so many programmers use the hexadecimal number system.

Sometimes it’s clear why. For example, when the error code is 970 (10), it is easier to write 3CA (16)), it is just convenient and understandable.

BUT, for example, when small numbers are translated into a hexadecimal system, then I don’t understand this.

For example, constants:
const OP_INSERT = 0x01;
const OP_UPDATE = 0x02;
const OP_DELETE = 0x04;

etc., isn’t it easier and clearer to write in decimal notation?

Please tell me why and why it is used?