It seems like a more helpful answer is that the Oriental churches are used to changing things without the consensus of one another, while the Orthodox are used to doing things together. The Orthodox Churches share a common liturgy and calendar, while the Orientals are diverse in every way. They have their own distinctive indigenous liturgies, as well as local variations in things like major feast days. I think they're just used to handling absolutely everything on a local level, and very seldom even communicating with the other churches in their communion. Just a guess.
I don't think this is entirely/very accurate. It is not that things have changed, it is that things were always diverse. Within the Byzantine communion a uniformity was centrally imposed, as it was in the West. The diversity within our Orthodox Church is only that which was always there in all of the early Churches. The Byzantine communion only shares a common liturgy because the other local traditions were swept away in the Middle Ages.
There was always a centralising tendency in some areas of the Church. Leo of Rome wrote in a friendly manner to St Dioscorus, but within his letter still tried to impose several Roman liturgical customs as being universally obligatory. When Egeria visited Jerusalem what she saw was a different liturgical tradition to that which she was used to. It seems to me that this diversity was the universal custom, and reflected the inculturation of the One, Holy, Catholic and Apostolic Church in different cultures and places. It was only much later, in East and West, that a uniformity was imposed, that there is a uniformity in Catholic and Byzantine communities does not mean it was always there.