Its more complicated than @4matter may imagine. But becoming a "money handling business" isn't the hardest thing to do- just needs to be sufficient motivation to do so.
I've been taking a hard look at building a few front ends to Sia coin to make it more accessible to "normal people". Sia needs to become more production ready before it truly makes sense. (It looks like the devs are well on their way to making this happen though)
You'd essentially need to create a pseudo exchange, your own storage pool/set of hosts and a dropbox style client for it to truly be a good solution. From a liability stand point you'd need to provide your own hosts, and vet any 3rd party hosts if you want to go that route.
Right now if you lose files you just lose your sia collateral- if you replaced this with hard USD you'd potentially have to deal with the liability of losing someone elses files. In theory this is not a big deal with contracts in place. However- after owning a datacenter for 7 years I can tell you this never works out the way you'd like. You eventually lose someones information- and lawsuits ensue. Implied merchant-ability is not fun. We won the law suit but it took 2 years and 250k to settle the score.
The other issue of building a production worthy product for normals on Sia is what it would do to the network as a whole. If I add 800TB to the network- and I'm receiving an outsized benefit because I'm front ending all the contracts to make sure my servers are used is that fair? It'd massively blow up the block chain. All it would take is an enterprise sales guy working for a few months to end up with close to a Petabyte in essentially a silo within the network.
I'd like to see Sia compete with all the big storage providers- but what makes sense for the consumer is what created these centralized datacenters to begin with- the spirit of the internet has always been decentralized- so everything Sia does needs to stay true to that ethos.