At the risk of getting too serious after a quick quip about Lewes (as I'm missing their celebrations, now I no longer live in the area), but as you chose to say that as a reply to my comment, I'll try to answer it:
> they're both holidays in the sense that people treat them as special and celebrate them
We celebrate some things with a holiday but we don't make all celebrations into a holiday.
You can stop reading now, that was the gist of it, but I'm lying awake now, so I'll keep tapping away:
At base, a "holiday" is a day off work - you can guess at how it got that name. Nowadays, different places have a different selection of days that are National Holidays[1], when you expect to be off work (or get double- or triple- time). For example, in England, Easter provides us with two holidays but we don't have have All Saints or All Souls National Holidays. We also have a few holidays that aren't directly based on religious observances - May Bank Holiday, for example.
The days that are set as National Holidays have a historical basis to them far more than a religious one; any question as to "why this day and not that" has no more "meaningful" answer than "well, this happened in history and now we get a holiday, enjoy it".
As well as those National days, so long as you've got the time accrued, you are at liberty to take any of your personal holidays at a time that coincides with any event you feel like. So you could habitually take Halloween as a holiday, if you so desired. Many people will decide to regularly take off as holiday days that are meaningful to their religions; they still get to have the National Holidays as well (or work them for extra time, as anyone else can).
>... If you don't think one is, I'm curious why you think the other is...
Nope, sorry, you lost me there, maybe you're meant to aim that at someone else?
> I'm not sure why people object to the existence of multiple holidays and treats it as insulting the one they care most about.
The best I can come up as an answer to that is simply that, in the UK there really is just one long celebration over the Winter, which is "Christmas and New Year" - even though it has been increasingly eroded (come on, we *all* know the song "12 Days of Christmas", so why are so many people in a rush to chuck the tree out on Boxing Day?) and we only (only!) get three actual National Holidays in there now, instead of the whole lot (well, the servants didn't get the holidays, but they had an extra half a groat and a turnip, stop complaining), the cards still say "Merry Christmas and a Happy New Year": the celebrations can continue, a bit each and every day (often with a particular blowout at the start and near the end).
Other countries have other, a multiple, holidays in the Autumn & Winter, and all the best to them. Have fun.
But over here, just the singular holiday, which, like the classic Summer hols, actually spreads over more than one day.
The actual objections, when not made in jest, are then more about cultural imperialism when it seems we Brits are supposed to be doing what other countries do or expected to pander to a perceived inability on their part to admit that different places do different things.
[1] the proper name for a National Holiday is, of course, Bank Holiday.