The Short Answer Is That It Is Your Option
There are advantages and disadvantages to both.
If you leave the soaker hose on top of the ground, it will not rot out as fast and you can immediately see whether it is working or not.
If you bury the soaker hose, it is not as likely to be damaged by lawn tools or equipment such as mowers or edgers. I prefer that be left on the surface. If you choose to bury it, keep it shallow, say, just underneath the mulch.