If you look at their site, these are the mods designed primarily to work with UE.
Of the 10, 9 are included in the modpack (I assume the last one is missing because of lack of permissions). The pack is designed exclusively to feature mods that run on Universal Electricity. To add anything else would dilute the pack's intent.
Railcraft is included mainly for convenience, especially regarding acquiring steel. It also happens to be another mod that implements UE.
That all said, more recent versions of many of the mods have begun integrating IC2 support, so the chances of UE mods making their way into general modpacks is already a lot higher than it used to be.
Of the 10, 9 are included in the modpack (I assume the last one is missing because of lack of permissions). The pack is designed exclusively to feature mods that run on Universal Electricity. To add anything else would dilute the pack's intent.
Railcraft is included mainly for convenience, especially regarding acquiring steel. It also happens to be another mod that implements UE.
That all said, more recent versions of many of the mods have begun integrating IC2 support, so the chances of UE mods making their way into general modpacks is already a lot higher than it used to be.