Ease of adding leads to Subsequence

It seems overly complicated just to add a lead to a subsequence to have it follow up automatically. For one, all the potential issues as mentioned above (might not fire if they've been added to another sub already, won't fire if the campaign isn't active, etc.).

Also, for some reason the subsequences require a trigger. What if I don't use automatic triggers and just add leads manually? (which is what I do).