People compare the hypothetical side-loading they hope to see on iOS devices to side-loading app.s on Mac, but that's a poor comparison because Macs are a small target for malware type attacks due to being a low % of the personal computer market.
The proper comparator is side-loading on a Windows PC.
For years, people who used a Windows PC on the Internet without 'anti-virus' software were seen as risk taking fools, but it happened. Eventually Microsoft bundled Windows Defender to provide at least basic protection, and it was seen as better than nothing but you really ought to get a stand alone anti-malware app. (e.g.: Norton, McAfee, Bit Defender, etc...).
Before anybody tells me you can get good free Windows antivirus software, I tried that before, and the frequent, persistent pestering ads to sow fear/uncertainty/doubt to upgrade to their paid version were miserable to deal with.
So malware wasn't Microsoft's fault, but they had to deal with it, and end users still needed to deal with it themselves. PCs are often sold with a 'free trial' of such hoping to rope us into buying subscription fees for years, and have you seen the default a Norton comprehensive protection plan can hit an ignorant newbie for? Ridiculous, compared to the cost of the Windows notebook it came on.
iOS is a big market, high visibility player very likely to have owner financial info. on it. Big target for malware! So, some questions...
1.) What is the computing sophistication level of the average iPhone vs. Windows user? Concepts like trojans, phishing, spoofing e-mail addresses, etc...?
2.) Any idea what % of iPhone (and for that matter Android) phones have anti-malware software?
3.) How many people already paying for it bother to put it on their iOS device? For example, if you have BitDefender on your Mac, your package might include free protection for your iPhone. But how many devices? Did you do it? How many users wouldn't?
With this talk about opening up platforms, increasing competition and hypothetically lowering prices, beware the Law on Unintended Consequences, least you...
1.) Create a more fertile playing field for malware.
2.) Cause more malware headaches for users due to malware proliferation.
3.) Create a de factor necessity to pay for anti-malware packages with subscriptions into perpetuity.
My point is, if you think tearing down the 'wall' of Apple's iOS walled garden is going to help end users overall, don't be so sure.
Everyone with a device in their possession and they don’t like what it does, the company didn’t force them, didn’t poke them with a pointed stick, to purchase it. They just said, “Hey, wanna buy this?” If they have certain requirements that a device should have and they IGNORED their requirements and bought it anyway, well, they shouldn’t have ignored their requirements.