These are excellent questions and points and I'd love to know the answers to all of them myself.
Recently we had a discussion on this and it was explained that for PCs and the Internet, much of it was legacy protocols and connection methodologies never intended for public use. There was too much of an installed base now to change it.
However, that explanation doesn't apply to cell phone macros which is all new technology. As stated, the experience of remote sabotage was well known.
My own speculation is that cell phone providers allowed this because (1) they want their phones to be easy yet sophisticated for non-technical users and (2) easy automated features encouarge callers to make use of them consuming toll minutes and feature charges which leads to profits.
Let's face, pretty much everything we do in Windows could be done in upgraded DOS, and not that hard with pre-written .BAT files or menu screens. But the old "C:>" and typing in a command with proper syntax and operands terrified people. If we required lay users to go through a step-by-step process to download procs, music, messages, etc., on their cell phones they wouldn't bother and wouldn't like it. Face it, the everyday user _wants_ things to be automated. Thus our dilemma.
My cell provider mails me new shortcut services all the time, available for a small fee and airtime. Those small $1 fees can add up. (Should cell phone directory assistance really cost $1.25 per use, plus airtime?)