Here are two videos of an Icelandic Horse show. The first is regular classes, the second is of loose-rein tolt. Notice the differences in how the horse carries himself, and how he reacts to the bit, in each video.
In the first video, notice the horses tossing the head, shaking it, pumping it up and down, trying to open the mouth, holding the head at odd angles, going way above the bit, or way behind the bit.
If the Icelandic Horse is able to tolt without the heavy contact, why would riders want to go back to having the horse fight the bit?
Who is teaching people to ride like this? and who is allowing this type of negative impact on the Icelandic Horse?
In the second video, the horses are in more relaxed frames, able to carry their heads where they need them, and there is no fighting the bit.