I agree with you - for first 2 or 3 years of intraday trading - stay with one or two only pairs
What then happens - after you have taken a few thousand live trades - you start to then look at trading 3 -5 pairs - with the aim of getting more "free trades" on 30% stakes with stop in profit.
I never try and scalp more than 3 pairs at same time - more comfortable with just 2 pairs - but to actually have 30% trades in 3 to 6 pairs is then easier - with no stress - as what ever happens its always a win / win result
Also some days the one pair you focus on - might be the worse trading pair of the day - so thats why you need to be checking out others to compliment as well
But - its step by step first - and then over time with more experience - knowledge - confidence etc etc - you can slowly then start walking faster etc etc
Regards
F