Zero is not rock bottom. A lot of stores of value have negative returns. Zero is high in a lot of contexts.
Historically, negative real returns on stores of value were the norm. Before financial systems existed, almost all investments had negative returns if you didn’t put work and energy into them. To store value, you had to accumulate stuff, buildings or land. Most options either had high maintenance costs, were subject to risk of damage from natural causes and theft, were very volatile or required hard labor to get production out of.
Even in societies with financial systems, getting low risk, hassle free, liquid, positive real returns has been difficult for most of history. This just reflects the natural laws of thermodynamics that tell us that everything tends to decay without a constant supply of work and energy. In general, most things require maintenance to keep their worth.
The 20th century was probably the most notable exception. Because of unprecedented demographic and technological growth, positive risk free real returns were easy to find. The recency effect probably explains some of the confusion people have about this. It is possible that under favorable conditions, wealth can have positive returns and even compound into very good long run returns but it is not a guarantee and there is nothing natural about it. It may not continue forever, particularly amidst an aging and retiring population in a world no longer as rich in easy to exploit natural resources.
While people are used to get negative returns on very short term purchases, you buy fresh vegetables at the supermarket, even if they degrade over time, many can’t seem to accept the normalcy of negative returns on longer term assets. In nature, squirrels’ nut caches have a certain percentage of losses from theft and spoilage. Real returns tending towards the negative is natural even if they can seem unusual for people just out of the 20th century.