Why does soil grow weeds?
From looking at many plots where rotovators are frequently used, the answer has to be partly that soil is recovering from cultivation by re-covering with weeds. I see so much chickweed above all where rotovators are used, compared to none at all on my own plot.
Rotovating may seem an easy solution to clearing ground and making a tilth for sowing, but it causes far more work after that. It is better to either hand weed carefully and spread some compost, then keep heoing and weeding until your soil is clean (yes, really clean and a joy to garden!), or to do an initial mulch of really weedy soil or pasture, using some compost and or manure with a light excluding mulch on top.