This is a thing. People buy it to force others to stay away from them.
Logic of such a thing aside...
Actually, no. The logic is fucking horrendous.
However, I'm not all that afraid of the notion of human porcupines commuting within eye's reach.
No, I am afraid of what happens next. What if these become popular?
Some people begin buying them in order to counter all those who don the spikes.
Until someone starts wearing actual armour.
Then the arms race begins.The cat spikes soon get replaced with splintered wood spikes to counter kevlar fencing suits and leather biker jackets. People begin upgrading their armours with chainmail and segments of random bolted metal. Gangs form with people driving rival uniformed commuters off with travel pikes and cuirasses to counter their now newly-forged steel spikes.
Then someone gets high-tech.
People striding around in mechanized suits, impervious to all but power spikes on their daily travels. People begin engineering super-human commuters and start invading other stations to control trade routes. The train lines become the new silk road, Empires start forming on these lines of wealth. Incentives to start developing more and more powerful armours increase as the factions begin consolidating their power.
And then it happens. Something ticks. The factions fight. Globally, an international linked railway with every Empire fighting one another for supremacy.
Two outcomes are possible. Global devastation...
...Or the reign of the God-Armour of mankind begins.