First, 90% of arbitration is between firms, not consumers. Consumer driven arbitration is rare enough that it's hard to specialize as a pro-business arbiter. Usually arbiter bias will be pro [big, small, old, new] just like us regular people.
Second, like other public facing retail and service management, consumer disputes are generally 80% frivolous. Like "they did not read the contract" level issues. That about 50% of disputes award in favor of the consumer is seen as overly benevolent appeasement.
Note: the 20% non-frivolous are usually very clear cases of the corporate participant blatantly or maliciously screwing up; no sympathy there. People are people everywhere.
For this reason most industry professionals very strongly suggest mediation rather than arbitration. It's quicker, cheaper, and usually ends in a voluntary non-binding settlement. And if you don't like it, it's non-binding; you can proceed to arbitration. Corporate clients would usually prefer to voluntarily agree to a settlement to make the problem go away, and consumers get the neutral information they need to understand why they misunderstood the situation.
However, most people see red and want to punish the other side. That rage makes them want to use as much authority and leverage as they can. Arbitration is seen as "not enough of a punishment, court would be better." When really, most people would be better served sitting down and talking things over with mediation rather than explicit adversarial intent.
I've heard similar things from civil court judges. They don't think they're biased for or against citizens, police, lawyers, etc. They are used to seeing the most incompetent petty facepalm justifications to "punish" someone, instead of seek justice or restitution. They are biased positively towards anyone who shows the slightest decorum, competence, or noble intent.