How do you know it means that.. many people go barefoot and just keep sandles for in the towns or on harder tracks..
Fishermen and farmers wouldn't have worn sandles on boats or in mud.. Sandles were a luxury. That's how I would understand it, and they would be unlikely to have extra pairs anyway. These were poor people.
It’s true that there were some who didn’t wear sandals because of poverty (cf. Luke 15:22) and that there were instances where it would be impractical to wear, but to say that sandals were a luxury is not right. Sandals were common throughout Biblical times. We can know this from history, from how the church has understood this passage from early times, and from the Bible itself.
Let me give you a few example from the Bible:
Moses was keeping a flock when God told him to remove his sandals because the ground was holy. (Exodus 3)
In the Exodus account, God commanded His people the Israelites to eat the Passover meal while wearing sandals. They were slaves of Egypt at this point but about to be set free and therefore to be ready to leave in a hurry. (Exodus 12)
The Gibeonites deliberately wore worn and patched sandals in order to appear as if they had travelled far. (Joshua 9)
John the Baptist expresses Jesus’ superiority by saying that he is not worthy to even untie Jesus’ sandals. To remove a person sandals implies serving as a lowly servant. It comes from the fact that these servants would take off their master’s sandals, carry them, and wash their master’s feet. John is using this common illustration to rightly express his humility before the Lord. (Luke 3)
Peter was in prison but upon being rescued by an angel was told to dress and put on his sandals. (Acts 12)
Perhaps the clearest text we can cross-reference is Jesus’ sending of His twelve disciples in Mark 6:8-9: “Jesus charged them to take nothing for their journey except a staff — no bread, no bag, no money in their belts — but
to wear sandals and not put on two tunics.”
In brief, knowing that sandals were common, both in OT times and in NT times, and comparing Jesus’ words to the seventy (or seventy-two) with His words to the twelve, we can understand that Jesus is not demanding that His disciples are to go barefoot, but rather to trust in the Lord and His good promises. God will provide for our needs. We can find the same promise which is given to all who believe in Jesus, even us in our time, in the Lord’s Prayer. Thanks be to God!
Hope this helps! God bless!