It may come as no surprise to many, but there are .gov regulations about almost every facet of railroading, and grade crossing signals are no exception. The details are far too lengthy and complex to detail here, but to name just a few there are standards for how many flashes per minute, how much advance warning must be provided, how long it takes for gates to come down, how often various components must be inspected and tested, and just about anything else you can think of. There are regulations on how the equipment is designed, and how it actually functions.
These regs and standards are the result of years - decades - of testing and use, and the FRA has inspectors visiting railroads constantly to ensure compliance.
No railroad is going to arbitrarily start putting lights here or there outside the scope of the regs. To do so would invite incredible liability issues. If someone were hurt, the plaintiff's attorneys would have a field day with "it's not bright enough", "it's confusing", "you didn't do it to ALL the crossings", "it's distracting", and anything else you can possibly dream of. A railroad's best approach is to follow every regulation there is to the best of their ability and leave it at that.
And let's not forget that existing laws in every state impose the responsibility on the motorist to yield to an approaching train. While more and more crossings are receiving active protection (flashers, gates), the plain old crossbuck still is the same as a yield sign. I'm trying to stay general in nature but will say I believe one of the pics of this wreck showed a "STOP" sign on the crossbuck pole. It could be argued this was not much different that if the truck had entered a highway after a STOP sign when it was not safe to do so.
The railroad which owns and maintains the infrastructure does have an obligation to comply with rules and regulations. But that alone cannot ensure every motorist will do THEIR part as well. Sadly, tragically, it only takes one failure to produce fatal results.