There are pros and cons to the players card debate and I think a player needs to weight them based on his/her own circumstances. Here are some things to consider both ways.
Some pros are obviously playing rated may produce some additional EV. You may get some sort of mailer with free bet or match play offers that serve as direct EV. You may generate points that can be turned into cash or some sort of free play which would also be direct additional EV. You may get some sort of food offers ($xx food credit, free buffets or even 2for1 buffets), that I would call indirect EV, if it saves you money you would otherwise spend on food. If you travel far to play and end up paying for a room, that same indirect EV can work if you get free or discounted room offers.
This kind of additional EV, can be particularly beneficial to a lower limit player and/or a player trying to grow his/her BR. BUT, the problem is that most casinos don't offer much anymore for blackjack play and especially at lower limits. Some casinos no longer even rate you at low limits.
Now the cons, playing rated means the casino has your personal information. It also means they have a record of your play and if you are a winning player, playing a winning game, that can quickly and easily become obvious. When playing rated, players often start ratholing chips to try to hide that they are a winning player. And that has the potential to backfire quite severely. If a casino suspects you of ratholing and notes it on your record, you will then be "credited" with any and all chips that they otherwise can't account for. That is the last thing you want, so I would be very careful with any ratholing. I think the best ratholing technique is to combine with bathroom break "wong out", and simply rathole just a couple green (never black) chips in the bathroom, out of sight from camera. You only need to rat hole EV or slightly more. Most players do way too much.
If you are a player that most of your play takes place at a small number of casinos, you become somewhat "known" and playing unrated probably doesn't even buy you anything. In that situation, the casino is likely still tracking your play, even if you play unrated. They simply assign some sort of code name to you, so you are losing any benefit from playing unrated and might as well get what additional EV you can. Also at a local type place, playing unrated stands out a little more. Most players want whatever comp and freebies they get. Someone refusing is a little odd. Where if you are playing Vegas or somewhere like that, it isn't nearly as unusual to play unrated. You can give all sorts of excuses like I would be back for a long time, to I only have a few minutes.
So like most things there is no one right answer. Jjust figure out what works for you and your situation, weigh the pros and cons.