Probably because the other things are a known quantity, and happening regularly they can be allowed for. Covid-19, SARS, MERS, Ebola and the like are unknowns (or began as unknowns) so it is impossible to make similar allowances for them. It's not feasible economically to build and maintain an excessive number of hospitals "just in case" so at times there will not be enough of them available through normal means. And with unknowns like these, you can't predict infection and death rates; they can only be discovered as things happen. There are many other far more deadly diseases which occur in great numbers, but those do not often affect otherwise normally healthy people like this disease does, which is one of the things which makes Covid-19 so bad.
As best I can find, the percentage of deaths from Covid-19 does not exceed 5% and the usual numbers given are considerably lower. This is not a bad mortality rate in itself, but the numbers of people who will catch Covid-19 are so high that the total number of fatalities will be substantially larger than what we see with other diseases which have a higher mortality rate. It's these total numbers which makes this disease so problematic, not the percentages of deaths which come from it.
Phil
The biggest problem in Wuhan was that they had no idea of the infection rate or death rate, so they had no choice but to build the field hospitals, and also to slow the infection rate by isolation. Both measures worked, and now their new field hospitals are out of a job, unless they decide to relax the isolation in order to build up herd immunity, in which case the new hospitals will allow them to get there faster.
For countries where it has recently arrived, they do roughly know the infection and death rates, so they can choose how much extra hospital capacity to build, possibly zero, and control the infection rate through isolation to fill the hospitals, but not over fill them.
There was someone on the news last night saying UK should immediately take drastic isolation measures to cut the infection rate and that herd immunity was a highly dangerous strategy, but what was his alternative? Turned out to be to lock everything down completely until we develop a vaccine. Unfortunately, we don't have coronavirus vaccines for any of the common cold strains despite trying for a century, there is no reason to think we will definitely get an effective one within 10 years, some people are optimistic for one next year, but very often medical research optimism doesn't produce results, how many years have we been working on an HIV vaccine? Realistically, all countries are going to achieve herd immunity, even if they don't try to do so, or if they work against doing so as some currently are, so planning to achieve it the most sensible option. For most countries it also makes sense to properly isolate the elderly and otherwise vulnerable until herd immunity is reached, so far most countries have failed to do so effectively, although it may well explain the very low death rates in Nordic countries. In some countries there have also been problems with younger people, quite likely explained by high smoking rates.
I dunno if I'd advocate such a measure, might be better and quicker to re-purpose sporting halls or fair/Exhibition building like they are doing in Europe (these venues they will not be used for quite some time, it's a win-win solution)
Can be difficult to isolate people in such places, taking over university facilities where there are often a lot of medium sized spaces close together which can be isolated and ventilated would be a better bet. Isolation and ventilation are important since your chances, and rate, of recovery depend on how much virus you are continuously exposed to. Our health secretary pointed out today that if everything is in lockdown then we have plenty of empty hotels, where each patient can be isolated in their own room.
WTF goes on in these people's heads? Sheesh...
Plenty of canned goods like beans and still a lot of soups, fresh meats, milk, and cheeses. Almost nobody at restaurants or fast-food joints. Very little traffic on the roads compared to normal.