This comment makes the assumption that the software is cloud based and all that matters is uptime.
I used to work on a backup application, it ran locally on our clients' machines. We had over 10000 clients. A 99.9% reliability would mean that there are 10 of our customers, at any one point, having a problem. It's not a question of uptime. It's a question of data integrity in this case. So 99.9% reliability could even leave us open to, potentially, 10 lawsuits. Also, about 10 support calls per day.
Now we only had about 10k customers at the time. Imagine if it were millions.
I used to work on a backup application, it ran locally on our clients' machines. We had over 10000 clients. A 99.9% reliability would mean that there are 10 of our customers, at any one point, having a problem. It's not a question of uptime. It's a question of data integrity in this case. So 99.9% reliability could even leave us open to, potentially, 10 lawsuits. Also, about 10 support calls per day.
Now we only had about 10k customers at the time. Imagine if it were millions.