Do you have to? No, of course not. If you have never seen any activity before, it is not likely to happen all of a sudden. Granted, now is the easiest time to do it so you could ask yourself how you would feel if you lost some plants or how you would feel about digging all that soil out to do it at a later date.

I do have some gopher activity. Some of my beds are lined with chicken wire and some are not. There was just not enough energy or money to line all of my beds. I just make sure my most important and expensive plants (roses and trees mainly) have a wire basket.

I decided not to do wire. I did cardboard and soil and time will surely tell. I am doing a vegetable garden in these boxes so now my thoughts turn to border fencing for the bunnies and other potential thieves. lol

If you see ANY gopher activity in your neighborhood, I would line it with the Hardware cloth/gopher wire! Chicken wire is too large holes and is also too thin and will rot out in a couple of years (unless you put multiple layers, but still...better safe than sorry!)
Look at that large pile of dirt, and think of digging it in first, then out and in again!
Just noticed you already went without. Good luck to you and keep an eye out for those critters! Keep the above in mind for future beds, though, if you end up with gophers. Nancy

...any gopher activity in neighborhood...

I second that advice. We didn't have moles across the driveway to the edible garden area, so thought they surely won't burrow under the gravel driveway & didn't line the wood frames with wire. Now it's been a frustration as the crafty critters found the boxes of earthworm rich soil delightful. Thankfully, we don't have gophers in our area.

I never had voles, moles or gophers until this year. The voles took out my 3-year old asparagus, then went on to beets. I was ready to empty my raised beds to put down hardware cloth, BUT...

Hardware cloth is really expensive, and the holes in chicken wire are too large to keep anything out.

Then I found that Irish Spring soap is so offensive to sensitive noses that it keeps the voles out. Cut bars into chunks and place them around the outside of the raised bed, preferably under mulch. They will head the other way.