Deflation can be devastating to those in debt. If you take out a loan for a house or a tractor, then subsequently discovering that you have to pay back substantially more than you borrowed (before even factoring in interest!) could be quite a shock.
To give a simplified example, if a farmer takes out a $50k loan, then at current prices they might be thinking that can be repaid by selling 10,000 bushels of produce at $5/bushel. However, if there is subsequently 20% deflation, then the price would fall to $4/bushel and the farmer would all of a sudden find they have to sell an additional 2500 bushels to get out of debt. If they can't, they risk losing everything to foreclosure.
Exactly - in a deflationary world debt would be far less common. There would be much wider and typical use of equity, and innovations around equity to make it as common as debt is today.
To give a simplified example, if a farmer takes out a $50k loan, then at current prices they might be thinking that can be repaid by selling 10,000 bushels of produce at $5/bushel. However, if there is subsequently 20% deflation, then the price would fall to $4/bushel and the farmer would all of a sudden find they have to sell an additional 2500 bushels to get out of debt. If they can't, they risk losing everything to foreclosure.