I think I would have predicted that they'd need to run at a very large scale, and be able to handle massive spikes. Whether or not I could have convinced them to make the investment is another story.
It's a gamble no matter what, but moving too quickly or moving too slowly results in the company going under.
In that case, I think straddling the line of "overwhelmed when there is a big spike" is a good spot to be in all things consitered.
Currently they are signing people up at a dramatic rate despite their server issues. If they start laying people off because they spun up to fast they could start a panic that would kill them.
They have to weigh all of this in when deciding on an infrastructure spend.
I would also like to think from a purely personal level that they don't want to hire and fire people like that as these are real people with real families involved.