One big difference is that there's competition between cash handling providers, while there's essentially zero wiggle room for interchange fees.
That's what makes interchange and network fees so much more problematic than acquiring fees. There's very healthy competition between credit card acquirers and payment service providers on both features and price, but in the end, you have to accept whatever card your customer has or there won't be a transaction.
In the EU the authorities have recognized the power of the card networks and introduced price controls on interchange fees in 2015, capping them at 0.2% for debit cards and 0.3% for credit cards.
That's what makes interchange and network fees so much more problematic than acquiring fees. There's very healthy competition between credit card acquirers and payment service providers on both features and price, but in the end, you have to accept whatever card your customer has or there won't be a transaction.