The key to this is that insurance is not MANDATORY. You can still be your own bank if you want, but it's perfectly reasonable for someone that isn't comfortable securing digital assets to outsource that to someone else. As far as whether this will have a significant effect on adoption is at best speculation.

There are many reasons why someone would buy bitcoin, from using it to send money abroad to buying amazon things at a discount. A lot of use cases actually don't require any holding of the money for a significant period of time, which is the use case for insurance. As far as insurance services, the option expands the use cases, so it probably expands the number of people that would adopt.

If anything, I believe the ability to buy insurance on cryptocurrency investments would speed up adoption by making it less risky to traditional investors. Simply having insurance available doesn't mandate that everyone buy it; we'd all still have the choice whether we opt-in or not.

Traditional investments tend to have insurance policies on the insurance policiy of the insurance policy of the initial investment. While it's a somewhat yucky business, it's also a standard practice in today's financial ecosystem. Having these options available for bitcoin only strengthens bitcoin's value proposition and familiarity to traditional investors.

Insurance is one of many methods to transfer risk from one party to another. It adds cost because there is a price to pay for some third party to bear risk. If there information was perfectly symmetrical where everybody has access to same information then Insurance would be a zero-sum game.

There is always risk in everything you do. In the context of being your own bank maintaining your own private key for your Bitcoins. There are always potential accidents (e.g. your storage device containing your private key might break due to some erroneous error, the information in your USB key in some bank vault getting wiped as a consequence of an EMP). That's where Insurance comes in, it is for some person who wants to eliminate any possibility of loss to transfer this risk to some third party who is happy to carry this risk at some price.

Therefore, there's no reason to think why Insurance might slow the adoption of Bitcoin. Insurance should be available for anything where there is any risk whatsoever.