* The Myth of Uniqueness: Each and every company doing business believes that their business is different and couldn't possibly be the same as another company's. This is not completely untrue, but it's also not completely true. The problem is that this myth is propagated by the enterprise software vendors. The profit margins on services to customize software is far, far greater than the margins on software licenses. It is in vendors best interest to promote software customization.
* 50 Years of Customization is Hard to Throw Away: OK, maybe there's not many 50 year old systems running in production any more, but there are 25 year old systems. The amount of money spent to customize those systems over the years is enormous and big corps are not eager to toss that money spent away to start over.
* Database Conversion is Hard: Not so much difficult, but hard in the sense that it requires many, many hours to first clean up the old database, run the conversion, then validate the new data. One mistake could mean that someone's policy lapses because the conversion broke the automated Pre-Authorized Cheque processing code for that one client.
* Working at Big Corps is Uncool: Let's face it, being a programmer at a big bank or insurance company is perceived as boring. The over 40 set that these jobs appeal to aren't traditionally big adopters of new technology. As these people get promoted into decision making roles, they default to safe, known technologies.
* Corporate Partnerships: Big financial industry companies outsource their IT to corporations like IBM. These services companies have a vested interest in maintaining the status quo. It's much like bee-keeping bears ;)
* The old stuff still works: Even though the legacy code is unreadable and numbers in the millions of lines, it still mostly works. The "if it ain't broke, don't fix it" argument is an easy one to make when your executives (beholden to the shareholders) have to make their quarterly numbers.
Don't get me wrong, I'd love to see start-ups in the financial services software industry pop up with innovative solutions. In fact, I've thought about attempting this myself, given my background. But the elephant herd of legacy vendors to find your way around is extremely intimidating. In fact, I actually saw a few small vendors pop up over the years, get small contracts within the big insurance company to do something innovative with their shiny new technology (but not mission critical to the corporation), and then watch that company take on more and more lucrative services contracts further from their core software product. Eventually, their initial product offering becomes a footnote for them and they turn into something else, legacy related.