Yes it's sad but true. Personally I don't know why Jagex did this, but I'm sure they have their reasons.
I suppose the holiday drops and rare items show how long that someone has been playing, so you can show them off as an achievement. Or perhaps they don't like the fact that some people (Smart people) will hoard loads of holiday drops for themselves, buying them from anyone else that has them, or starting bogus accounts and collecting holiday drops, then when the holiday drop event is over and it's not longer possible to get them, the hoarder would charge a TON of money for each one. Since they're no longer available, people will pay big money for them.
Personally I don't think that it's a horrible thing, but it does present people with an opportunity to collect large ammounts of gold and sell it on ebay for example, that's a bad thing as it's against the rules and encourages people to use auto miners etc to gain gold.
Okay, now that we've established a bit of background information on the rare items in runescape, it's time to get down to the specifics of a few of the more popular holiday drops.
The most commonly talked about runescape rare item is the party hat, sometimes called phats for short. They come is 6 different colours, red, yellow, blue, green, white and purple.
Pretty bad graphics by it's one of the rare items in runescape and presumably it's value will constantly increase.
Another rare item is the santa hat. This was a christmas holiday drop in 2002. Again, very rare and highly priced. Not sure about how much it costs compared with the party hats.
And finally, the last tradeable runescape rare item holiday drop that I'm going to talk about, is the halloween masks. As far as I know there were only 3 colours and other than that, they looked exactly the same. It could have been picked up on halloween 2002.
In 2003 and beyond, holiday drops were made to be no longer tradeable, and will never be tradeable for the forseeable future. So if you want holiday drops you'll have to either shell out massive sums of money for the old ones that are tradeable, or wait until the next holiday event to be able to get your own, for free of course :) I hope that has helped you gain a bit of insight into the world of rare items and holiday drops in runescape. I also hope to teach you much more in the future, such as how to get a ton of money in runescape.