I have switched banks a couple of times too. In all cases, it has been because the bank took advantage of me when I made a mistake.
It has always been a variation on this same theme.
The last time I changed banks was in 2010.
I had made a mistake and I overdrew my account by $5 or so. That was obviously my fault and I should have been on the hook for one overdraft fee. My bank, reordered my transactions and caused me to incur 5 overdraft fees.
When I called in to complain, they "waived" two of them, leaving me to pay $90 when I should have only had to pay $30.
That was it for me. I opened an account at a Credit Union and left about $5 in the bank account so they'd have to keep paying to send me statements.
That went on for over a year until the bank implemented a $2/mo convenience fee for paper statements. In three months, my account was drained and the bank closed it.
People need to be willing to pick up and leave a bank if the relationship is no longer advantageous.
From the bank's perspective, it's always business and never personal. That's how you have to act in return.