Confused why web hosts offering big discount for 1 and 2 year term

Before I start want to make it clear that in no way am complaining, just like to know what the reasoning is for it.

Perhaps it is me being dumb but just cannot understand why web hosts offering big discounts if sign up for 1 or 2 years contract on the Reseller Hosting

I would have thought that having regular monthly income from your customers would be better than receiving one payment every 1 or 2 years

If can offer the big discounts for the 1 or 2 year term then why are the monthly ones so much more (over 50% difference in some cases)

By having regular monthly income from your customers means you can plan exactly what you are doing as there must be times when no one signs up and so no income at all

Yes, I know some customers will only sign up on a monthly basis but does it really make a difference and enough to still keep enough income to keep you going

Eventually at some point in future there will be no one left to sign up for the offers, where will your customers stand then as no income means cannot pay wages, bills etc, will you just shut down and disappear ?

I remember signing up for someone for 12 months a long time ago and within 2 months they just disappeared (yet they had been going for a few years and had fair reviews at the time) and was left out of pocket and no way to get a backup of anything.

What happens if staff leave or have to lay staff off because not enough money coming in, can you still guarantee that customers will not suffer

Sorry if questions sound dumb but am not talking a few $ difference in monthly and 1 or 2 year terms, I am talking a big difference in price

Can someone explain the reasoning and help me understand

Please, no one take any offence as am not complaining and am not trying to offend anyone and really would like other peroples views on this (especially the web hosts offering reseller packages)

Thanking everyone in advance