Handy Haversack vs. Bag of Holding

The Bag of Holding (DMG pg.153) is an uncommon magic item and has a significantly greater volume than any of the pouches (or even all combined) of Heward’s Handy Haversack (DMG pg.174), which is rare.

My confusion stems from the fact that, while the Bag of Holding is obviously superior to Heward’s Handy Haversack, it’s the more common item of the two. Why is that?

Some other info to consider:

In terms of fluff, the Bag is depicted as a simple satchel while the Haversack is depicted as a hiker’s backpack with multiple straps and pouches. The Bag also has the disadvantage of looking similar to the Bag of Devouring. Regardless of contents, the Bag weighs 15 lbs. While the Haversack only weighs 5 (and I highly doubt 10 lbs. of difference is worth a difference of category in rarity, especially making the Haversack rarer when the bag holds approx. 8X more volume. To say nothing of weight.).

Other than that, they have the same rules regarding their extra-dimensional properties, interaction etc.

If your answer is not directly from official sources (ex: “we know this is a typo because of existing errata, found here”), please remember Good/Bad Subjective and back your answer with evidence and personal experience.