>...pull the bed to the side of the road and it's gone within a day
That's littering. In most places this carries a substantial fine. Sure, you, might not get caught. I've known several tenants that got large disposal fee bills from their landlords for doing this. This happened whether they left their trash on the sidewalk, or by/in the bins.
>it's easy to buy one used in a new city. If you can afford to heat treat it, you can be sure theres no bed bugs, or if you have a job, buy a $200-$300 mattress from amazon - theyre surprisingly good these days.
Easy != free. Every expense adds up.
Deposit up front before getting back whatever's left after the previous landlord takes their scammy fees.
Lost wages. Costs of moving itself, and disposing of stuff that needs to be repurchased . Buying new stuff, even replacing a modest set of furnishings for a studio from second hand stores can pass $1k easily.
>no family, no savings, just a lot of manual labor/smart packing.
That has a price tag. You're not calculating it accurately. Just because you think you made all those moves cheaply doesn't mean you did.
Did you rent vehicles? Rebuy furniture? Stay at hotels? Mooch off friends or family? Did you eat out or sleep in your car?
These costs grow with a family. It might cost me $500 to move in a hurry. But it could cost a family $10k or more.
Did they stay long enough to build significant equity or make repairs? They might've lost money compared to renting. Some people do everything right and suffer bad luck forcing a move in bad conditions.
Do they need to rent or stay at hotels in between the move out and move in? It's not always possible to avoid this.
Even moving/re buying a minimal amount of furnishings for a family can cost thousands. Moving it is often cheaper. That adds time and labor either way. Or cost to avoid this. Some people also aren't physically capable of moving themselves.
It feels so easy and simple because you make these decisions for you and you alone.