Let's take a look at how this actually works with an example and some real numbers.
I'll pick MSIG's Hospital CashPlus mid-level Gold Plan as a reference example here, and we'll assume a 44 year old (unlucky age according to superstition) has a sudden heart attack with complications. It has to be sudden and unexpected -- no hint of heart disease -- otherwise the insurer won't pay anything (pre-existing condition). According to MOH data, the average hospital stay for that sort of medical problem is about 8 days. Let's artificially add 50%, or 12 days, of which 2 days are in the ICU.
OK, so what that 44 year old gets in exchange for paying her annual premium of $564 (eek!) is $400/day when in the ICU, $200/day in the hospital otherwise, and $500 because the stay exceeded 7 days. That's a whopping $3,300 total payout, and you have to pay $564/year in premiums to get it (44 year old in this example).
What the heck are you doing buying that sort of product? I don't get it. If a swing of $3,300 is going to wreck your life, then this policy won't fix that. A bigger emergency reserve fund will, and you're $564/year farther ahead in building up that emergency reserve if you don't buy this policy. That's because there are myriad reasons why you might not be able (or want to) work. Maybe a member of the family is traveling overseas and gets into trouble, and you have to fly there to help out for several days. That's not part of the deal for your $564.
Let's contrast this with an Integrated Shield plan rider that pays a hospital cash benefit if you voluntarily downgrade one ward class. Plus the rider itself reduces or eliminates deductibles/co-pays. I'll use Prudential as the random example here. Let's say that 44 year old has Prudential's PRUshield Plus (which covers public hospital A wards), and she decides to add the PRUextra Plus rider for $341/year (not $564/year). She then has her heart attack, with complications, and stays in a lovely air conditioned B1 public hospital ward for her 12 days. Her rider immediately eliminates her deductible and co-pays, meaning she avoids at least $2,500 of medical bills right off the bat. (That's her deductible in B1 ward under the main Integrated Shield policy.) For a 12 day stay (2 in ICU) in B1 ward she's probably going to see a bill in the $5,000+ range. Let's call it $5,000 (too low), so that's a minimum of $2,750 of rider benefit so far ($2,500 deductible plus $250 co-pay, i.e. 10% of the amount above the deductible). Then she also gets a flat $125/day cash payout because she stayed in B1 ward instead of A ward, so that's another $1,500. Plus she gets $30/day to accommodate a family member who stays with her, but let's not count that. So for $341/year (the premium for the PRUextra Plus rider), for the same heart attack with complications, her rider policy pays her $4,250 -- $950 more than MSIG's Gold hospital plan would have. And she saves $223/year in premiums. Better deal!
I'm not necessarily recommending an Integrated Shield plan rider either, but at least it's a wiser use of premium dollars. You can construct other scenarios and compare them, but suffice it to say I'm not a fan of "hospital plan" policies.