Limited capabilities in 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 most important indicators are the price of the software development, and the cost of the software maintenance. I imagine how User Experience is kept back in such cases. But when it comes to huge enterprises, I'll mention two web/mobile apps as examples, I can't believe that they can't afford to handle all functionalities of their services on mobiles 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 of its functions.

Ex. #2 Eurobet. If you try to log into the website through mobile or use their iOS app, you will not see a lot of per-event bets. Let's say that for a match from the most popular football (US based please read: soccer) 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.

Edit #1: Stackexchange has similar limitations too. I don't know on Android, but on iOS you can't handle reviews, badges, and probably something more that right now I don't quite remember.