In which case, the emphasis should perhaps be on making it safe, rather than banning (and I would argue that developing a movable, physical barrier could go a long way to achieving this for some electrification tasks).
It's not that simple though us it ?
If you take the MML between Kettering and Leicester as an example - it's a 2 track 100mph railway which has 4 TPH each way (at least, more with freight), which means you have to funnel 8 trains, at reduced speed, as well as ensuring those working trackside are clear and potentially pause what they are doing roughly every 7 minutes - that's hugely inefficient.
Whereas on a total block, those working trackside can focus on the job without being disrupted every few minutes.