Starting with $10 per week does not mean you must remain at that level for 20 years. That is an anomaly as we all aspire to grow in finances. Besides, it is at the current price of Bitcoin, $10 per week will really require so much time to realize a life-changing portfolio as I do not see Bitcoin doing X1000 easily. Therefore, to start with $10 per week requires that plans should also be in place to increase the inflow so that it will become easier to get 1 BTC which I consider something reason to hold for the future.
I think I will disagree with you on that, however when we talk about accumulating Bitcoin using $10 on a weekly basis, is actually based on what the investor is earning on a monthly salary, however we cannot expect someone who his salary barely take care of his needs to increase his accumulating amount because indirectly we are telling the person to invest aggressively.
We no that budging $10 for accumulating Bitcoin on weekly basis for 20 years is a bit small but perhaps that's the reason why DCA method was adopted because there people who may not be privileged to receive a higher pay salary but use as little as they can afford to accumulate, so if we consider the possibility of not being able to accumulate a huge amount of Bitcoin in the next 20 years using $10 is almost as good as telling the person not to invest until they have a reasonable amount.