It's not about the backup, or the data. When I buy something, I want it to last (especially if it is expensive), because I do not like paying for stuff that breaks soon.
Even if I make a backup three times a day, when the drive beaks, my computer crashes. Then, I have to order a new drive and wait a day for it to arrive (hopefully, the drive did not break on Friday afternoon). When it arrives, I have to install it, restore the backup and restart my PC. Oh, I also had to pay for the new drive.
Well, I could buy two drives and keep one as a spare, but then I will be paying twice the money for the same space and some part of the hassle still remains. On a desktop, I could use RAID1 but I would still need to buy two drives. Laptops usually do not have the space or the battery capacity to afford RAID1.
Same is true for other devices (for example power supplies).
Ok, here's a little economics for you: convenience costs money. Between the two extremes of paying as little as possible and having as little downtime as possible, you have to find a point where you are comfortable with the amount you are spending, the downtime you incur when it happens, and how predictable that downtime is. As you've placed yourself on the former extreme, you're saying that your personal time to recover from a downtime, and your ability to predict when that will be, is worth less to you than the money it would cost you to mitigate your situation.
SSDs cost more than HDDs, so I would expect them to last longer
Why on *earth* would you expect that? It's a *completely* different technology, with completely different failure modes.
(and since my hard drives are quite reliable, a SSD would have to work at least 10 years). As the technology is new, nobody knows how long SSDs will last, so I will have to wait and see.
The technology isn't that new: right now you can pay extra to get SSD drives which are guaranteed for a given number of writes. How long they last will depend on your usage patterns, but I've seen specs for drives which are guaranteed for *years* of continuous writes. Not only that, but *they'll tell you when they need replacing*.