* In larger companies, senior management may be completely inaccessible. Not "officially off-limits", mind you, but busy enough that you've got to deal with their assistants merely to get onto their calendar; and doing so may attract attention from their underlings (still at least one level above you), who may try to influence things before your meeting if they're aware of your agenda.
* Management ego: if the senior management in question has been in their position for quite a while, they may bristle when informed that their master plan has some holes in it.
* Management ego, part II: if you're relatively new to the company, you may have considerable difficulty getting buy-in from the old guard.
* Drowning new management: if senior management has recently undergone a turnover, the new kids in charge may be drinking from the firehose and unable to grasp the enormity of what you're saying. Or, worse, they rely on the input of a longtime company veteran whose "contributions" over the years may have directly caused the problem.
* Out of sight, out of mind: problems for you and your peers may be not be seen as a problem for senior management, especially if there is a great disparity in working environments. Work in a cube on a noisy floor while senior management has large, quiet offices on a different floor (or a different building)? They might not be sympathetic to complaints about your inability to concentrate.
* It's all about the Benjamins: ultimately, management is guided by two things. The first is money; if it's rolling in at the same or greater pace than last year, there is no problem. The second is risk; if you can't specify a specific risk to future business...again, there is no problem. Worse, if somebody can provide a toothless risk mitigation plan that sounds good but does nothing to actually solve your problem, then senior management may still consider the whole thing moot.
This is why many folks -- especially the ones who have been around long enough to have burnt by one of the above a few times -- simply advise suffering employees to look elsewhere.
It's not about apathy, it's about preservation of sanity.