Limited capabilities on mobile apps: why such choices?

As probably many of you, I use to experience limited capabilities in mobile apps. Until we talk about small websites and services, I got that probably they have to set some kind of cap where the indicators are the price of the software development, and the price of the software maintenance. But when we come to huge enterprises, I'll mention two mobile apps as examples, I can't believe that they can't afford to handle all functionalities of their services in mobile apps too.

Ex. #1 Paypal. With their mobile site/apps you can't handle controversies, you must log onto the website with a minimum requirement of 960px wide screen in order to surf the complete website and use all its functions.

Ex. #2 Eurobet. If you try to log into the website or use the mobile app, you will not see a lot of per-event bets. Let's say that for a match from the most popular football leagues such as Spain, England, Germany and Italy, you will have 50 betting options on the mobile app and 150 on the desktop website.

Now, until we talk about a small site running a Fantasy Football League for 1000 customers and earns €30000 an year, I won't expect they work on the mobile versions of site and apps in order for the customers to have full ease of use in mobility too. But the two examples I mentioned have both almost no limits of expense, I think, as they are both global money services with huge enterprises behind them.

So why would they choose that while in vacation I should struggle to get access to a PC to make my businesses as I'd like while at home? I am curious about what's the decisions leading to this type of choices, because as from my user point of view they make no sense for me.

I am sure some professionals in here, maybe customer relationships manager, maybe customer experience designer, might help me to solve this arcane.