A lot of the FDA regulations stem from the 1976 Safe Medical Devices Act. And it's a great example of how things can go wrong. It laid-out a pathway for approval of medical devices called "Substantial Equivalence" through something called the 510(k) process. Here's how reasonable it started: If you wanted to market a device that is substantially equivalent to something sold in 1976 or before, you simply had to notify FDA. If they didn't respond with an objection within 90 days, you were approved.
Then FDA got a flash of pure bureaucratic genius: If you ask a question about the application on day 89, you could then reset the 90-day counter and delay the approval. They had found a mechanism to delay approvals virtually forever. And when manufacturers started screaming over multi-year approvals, the answer was simple: FDA simply needed more funding. That's when they should have scrapped it and put a better system in place. But who's going to oppose safe medical devices? That's the beauty of the naming of these bills. Always pick a name that only evil people could possibly oppose.
So the new rub worked this way. Business-friendly administrations would either starve FDA funding or redirect their activities. A classic example was Bush II's de novo initiative. It was a way for devices that didn't technically qualify for 510(k) to have a lower-cost pathway than a PMA (PMA's can cost billions, whereas 510(k)'s are only hundreds of thousands). Less business-friendly administrations always announced crackdowns. Clinton's crackdown was appointing David Kessler, who was an absolute nightmare. Approval times for 510(k) went to years. If he hadn't overstepped and lost a supreme court case trying to get cigarettes reclassified as a drug delivery device, it would have been much worse.
The latest problem is enforcement. In the old days, FDA sent you 483 violations when you were out of compliance. If you really screwed-up, you got a warning letter. Warning letters were an absolute disaster. Used to be, a company would rather get a Federal Indictment than a warning letter. But now, they are sending-out warning letters left and right. It kicks-in a much more elaborate (and expensive) answer process, but what they've done is a two-fold mistake: 1) They've greatly increased both their and manufacturer's costs and 2) Diluted the impact of a warning letter. But what it does is lets FDA say: "We're cracking down. We've issued twice as many warning letters this year than under previous administrations."
And to answer your question about senators and congressmen, there's an unwritten rule. You can lobby all you want for changes to laws, but it's considered bad form to bring a congressman down on an agency. For example, if you called-out FDA on an administrative decision, you might win with the congressman on your side but you'd be facing yearly inspections and multi-year approvals on everything else. And yes, the non-political administrative personnel in these agencies 1) are essentially employed there forever 2) have long memories and 3) are very vindictive. It's weird too, because you can lobby like hell and make all kinds of noise legislatively, but it's still bad form to go outside that specific process.