[sanswork]

First two reasons I can think of.

Imagine you're doing that on an expensive cloud hosting setup and your expenses are really high. An infusion of capital could allow you the opportunity to build out your own server infrastructure(or pay annually on the cloud infrastructure) and dramatically lower your expenses and push your margins up a lot.

It would also offer you the flexibility in your funnel to offer back loaded deals to get larger clients onboard.

[syllogism]

An extra large EC2 instance is $360-$3311 per month. Maybe I have an imagination failure, but I can't see how cloud costs could be past 10k per month. So, how much could the infrastructure cost, and still be worth the investment?

Maybe I just don't understand the costs.

[sanswork]

First two ideas that spring to mind would be a realtime video encoding service and a CI service. In both cases your users to server ratio would be very low and in the first case your data costs would be very high. So you might be only making profit of $X per server per month even if your revenue is $XXX per server. When you're running your own servers you need a big investment up front but lower operational costs which is where the funding would come in.