Yeah, DCA can be very convenient for both rich and poor but I think it's not really the most convenient way to increase ones Bitcoin but rather it depends on the investor's capacity or level of income. Those investors who uses the long sum strategy may/can not consider this strategy because DCA is a gradual way of acculturating Bitcoin therefore a lot of consistency and discipline is required or needed in other to achieve the goal.
I disagree with you completely because you are viewing the DCA method as something meant for only low income people even though you started your statement correctly. DCA is all about the convenience it offers, not putting the investor under pressure or FOMO, not putting the investor in any anxiety as it does not care about the entry price and most importantly, it does not create the urge for quick sell off because it makes one think more about buying than selling. Big players like MicroStrategy used the DCA method to collect large quantity of Bitcoin to earn them the position of a whale, so why would you think that the DCA method is not a convenient way to increase the quantity of Bitcoin at ones portfolio?