But the problem is that for a lot of businesses, it just doesn’t make financial sense to set up their own decentralised systems

The exact opposite is true. For every company big enough to have any in-house IT capacities it's cheaper to do it yourself. There is a reason AWS and hundreds of similiar smaller comanies globally became a provider of computer services and server capacities: it developed as a side-gig from over-capacities in their own infrastructure. Infrastructure build because it made finacnial sense to set it up to themselves to save money and have actual control over their data and stuff.