The gemara says that in the merit of Avrohom Avinu comparing himself to dirt and ash, the Jewish people merited the parah aduma which involves ash and the Sotah which involves dirt. The Maharsha explains that it doesn't mean to say that had Avrohom not made the comment אנכי עפר ואפר, we would never have a way to remove the tu'mah of tu'mas meis and would never have a method for the Sotah would never have a method to return to her husband. Rather, there would have been a far more complex and difficult process to achieve these results. In the merit of Avrohom humbling himself with the statement of אנכי עפר ואפר, they were able to achieve these results in an easier form using mere dirt and ash.
I would add that the attribute that most greatly separates between people is that of arrogance. Humility is an attribute that breeds togetherness. In the merit of Avrohom's humility, we were zocheh to two mitzvos that bring people back together. The ashes of the para aduma allow tamei people to once again interact with the tahor, and the dirt of the sotah allows her back to her husband.
The gemara asks that the mitzvah of כסוי הדם should have also been in the merit of Avrohom comparing himself to dirt.The gemara responds that there has to be a tangible benefit that comes from the mitzvah, and by covering the blood there is no tangible benefit. It seems to me that Rava who is the person making the statement is li'shitaso. We find that Rava himself on 89a takes a position of מצות לאו ליהנות ניתנו, which simply means that the merit of the mitzvah in itself doesn't qualify as a benefit. Only physical benefits qualify as real הנאה. Therefore, Rava holds that the benefit of having a mitzvah to perform thereby an opportunity to receive reward in the world to come, doesn't qualify as a benefit and therefore isn't significant enough to be the reward for Avrohom's statement. It is only the physical and tangible benefit that come from פרה אדומה and עפר סוטה that can be the reward for Avrohom's statement.
As an aside, Rashi says that the ability to eat the meat cannot be considered the "benefit" of כסוי הדם since the kashrus of the meat is not at all dependent on kisuy ha'dam. The Pri Megadim (y.d.sifsei da'as 28:2) says that we cannot prove from here that it is permitted to eat the meat without kisuy ha'dam. Perhaps Rashi means to say that if there wouldn't have been a mitzvah to cover the blood, it would have been permissible to eat the meat, so we can't consider this mitzvah to be a real benefit. However, now that there is a mitzvah to cover the blood, it is entirely plausible that until it is done, the meat cannot be eaten. Nonetheless, l'ma'aseh we assume that the mitzvah of kisuy ha'dam has zero to do with the ability to eat the meat. Even if by tevilas keilim for example, the use of the vessel prior to tevila may be a bitul of the mitzvas aseh, by kisuy ha'dam the kashrus of the meat doesn't seem to be at all connected to the mitzvah on the blood.