I'm in a band with one 39-year old, and the rest of us are over 60. I'm 65. My past understanding has been that rock and roll bands memorize songs and don't go dragging music stands around. I'm the only member of this band that knows all the songs. We sound pretty good and have a small local following, but I hate to see people looking at cheat sheets and tablets and whatnot all the time.
Some of these songs are relatively challenging on bass, and since I don't read music (well, not really), I learn the parts and play them. Many of them have "signature" bass lines, like "Wild Night", and "Valerie" (I forget which version, but it's the faster one with the cool bass line, not the Mark Ronson arrangement), some Stevie Wonder tunes, and so on.
It's weird to me that after 18 mo. or so together, the lead singer forgets the words, the keyboardist plays chords wrong, and the guitarist has to look at his notebook between songs. Is it because pot's legal here? I don't understand.
We get a good reaction from the crowd, so maybe I should get over it, but I'm not bringing a stupid music stand. This isn't Lawrence Welk.
TLDR, but here's my two cents...
What you're describing sounds like a typical cover band nowadays... I'm not saying y'all aren't a good band. It's just become way more acceptable to use iPads, sheet music, and etc. on live gigs. Heck, I'm only 38 and even I remember a time when using music on stage was laughed at (for bar bands, rock bands, etc...). There's a few reasons for this, but it's besides the point of your post.
IME, if a current band, be it cover/tribute/originals or anything, wants to avoid using music on stage then it has to be an agreed-upon approach from the on set of the group. "We will not use music on stage, period." Otherwise it's very easy to slip into the habit of using music as a crutch and never getting passed it.
My last cover band had this exact problem. The rhythm guitar never practiced our songs and was always sloppy on stage. The lead female singer didn't memorize anything and even with a iPhone in her face was making constant mistakes. It was all fun and games for the first two years as we were building our rep., playing smaller gigs, and generally building our presence. However by year 3 we were starting to pick up much bigger gigs at larger venues with much higher pay.
The final straw for me was when I booked us a corporate gig at a BIG company pic-nic. A couple thousand for a full days worth. Months out I brought up at rehearsal that we need to be done with music and lyrics on stage. Everyone nonchalantly agreed, but I could tell it wasn't going to materialize. Rehearsals went on as I expected, same problems. When I brought up the issues the guitarist and female singer even started to become resentful with comments about how it didn't matter and etc... Frustration built. At the gig it went exactly how I knew it would go.
The final straw was afterwards when the company guy came to give me the check. Earlier we had played a Sublime song that both singer royally messed up on the lyrics. As I was being handed the check the guy says something like..."Love the Sublime, but your singers really need to learn the lyrics."
I quit a few days later.
Had I needed the money, I probably would have dealt with it, but this band was just a weekend warrior passion project. It was the first band that I started myself, so I learned a lot about running a band. But I was done dealing with the mediocrity. There were other issues that made it easier to step away, but I haven't looked back. Not that it matters, but since I left nearly two years ago that band has a played a total of 3 gigs at small bars. So that has been a bit of an ego-boost / validating.
ANYWAYS, my point is... No music on-stage needs to be an early phase decision. Getting the band to change course at this stage in the game will be very difficult. If it's something you're tired of dealing with, you might need to play hard ball.