On the operators side they get a lot of vacation divers on the cruise lines that may not be very experirenced or dove in quite some time (years.) They are covering their butts and possibly yours.
On the other hand if you are a fairly experienced diver and it has not been years since you dove and you feel comfortable with it you could have streched the truth a bit about your last dive.
I have seen the last dive time requirements run from 6 months to 2 years on cruise ship dives. I think it depends on the line and the dive op.
As a side note I always rent the pool at my LDS before I go on a cruise or diving trip in the winter. It helps me stay fresh with my skills and comfort in the water.
Yes, I understand why they would be conservative. I'm just wondering if this conservatism is increasing more recently as it dictates my strategy (refresher dive, etc)
As for your 2nd point, yes, I just learned that the hard way. I've logged over 30 dives in the last 15 years and do very conservative, guided dives.
I'm now looking into renting gear for a pool dive if I need to. Local dive shop has a "refresher" course that costs $75. This seems fine if I hadn't dove for a few years, but seems a little overkill since my list dive was just 18 months ago.