1. Because they can depreciate capex over a multi-year period. This can help manage the P&L better.

2. Likely because the bigger company has a much more complex balance sheet so applies more complex accounting to manage it.

3. It's not the development so much as what's being developed. You're essentially creating an asset rather than a consumable so the cost of that asset can (sometimes) be considered a capital expense.

4. Probably because that's how they're managing this for the rest of the firm. If all the activity is done consistently in one tool, it makes it a lot cheaper to manage than having to chase up multiple groups, massage the data, reconcile etc etc.

5. Depends on the org. It's finance who want this directly as will whatever levels care about their P&L.

It's also not inconceivable that there are standardised processes across the org so that engineering cares for engineering's sake. Though that doesn't sound like the reason in this case.

At the level of an individual team this may seem like a bad idea but, in an org with a lot of dev teams, fungibility of tooling and process can both be a big cost save as well as a big training save.