It used to be a good thing.
I just dug out our cheque receipts from when we put £20,000 into premium bonds back in 2006. Every month we would get 2, 3, or sometimes 4 or 5 envelopes drop through the letterbox. We only had it in there for a couple of years and eventually gave up recording the amounts won but it certainly beat having the same amount in the bank.
April 2006 - £100, £50
May - £50, £50, £50, £50
June - £50, £50, £50, £50
July - £50, £50, £50, £50, £50, £100
Aug - £50, £50, £50
Sept - £50, £50
Oct - £50, £50
Nov - Nil
Dec - Nil
Jan 2007 - £50, £50, £50, £100
Feb - £50, £50
March - £50, £50
Total for £20,000 invested over 12 months was £1700 = a return of 8.5%
£20,000 in a bank in March 2006 at standard base rate would have been around £1000 or 5% (rate rose to a max of 5.75% in 2007 then dropped away to 0.5% in 2009, and stayed there.