The simple answer in No.
You don't need to make reservations ahead of time.
But.....
This will no doubt cause some disagreeement ....
The reason people book ahead, is generally I believe, that they fear not getting a bed.
That is extremely rare.
There are always options, even if it means taxi to the next village. (never had to do that)
What the real fear is I think, is that they fear not gettng a bed of the 'type' they want or in a specific 'place' they want.
If you are prepared to be flexible, it becomes quite easy and actually liberating.
There are exceptions of course.
Roncesvalles and Zubiri in peak season are known choke points.
So booking those can make sense.
Or the final 100kms on the CF when very busy. (if you want private rooms)
Or during Samana Santa.
But 'normally'? No.
OK, Strong Opinion coming up!
Booking too far ahead, like 7-10 days locks you into a schedule that might not work for you for a multiple of reasons. Meeting others, wanting to walk further or less, injury etc.
Booking your whole Camino ahead, like 30-40 days is in my view sheer madness!
I have never met anyone who was able to keep to a schedule like that or was happy with a schedule like that. I've met plenty of unhappy Pilgrims though locked into a schedule like that.
They usually ended up using taxis back and forth for lots of reasons.
Confession.
I 'generally' book ahead.
But only a day or two.
Because I walk slow and usually arrive 2-4 hours after others.
And sometimes I'm keen to stay in a specific place.
But sometimes I might book on the day, as I see how I'm going.
Or not book at all. A donativo for example.
I did both on the
Camino Frances last May, when it was really busy, without any problem.
Nowhere I stayed was full.
You'll find there are lots of opinions on this !
Oh, and another place I HAD to book was a Municipal Albergue on top of a mountain.
Because theyn needed to send me the code for the door to get in!
No. That wasn't full either.
I was the only one there.