I think there are possible reasons to wait but on the whole there often isnt a need to. I had a very early loss and got pregnant only two weeks later. She is 2.5 year old now and we have an 11 month old boy too. My recent loss, baby made it to 9 weeks. I hemorrhaged badly and ended up very anemic so have to get my levels up a bit higher before TTC is a good idea otherwise I wouldnt wait. In my case I'm a bit older so I feel like waiting longer than needed is only adding risks.
One of the most convincing reasons that might make me consider waiting is that sometimes there is a small amount of tissue left which will likely pass naturally with your next period. From what I understand it is quite unlikely that there is anything left if your bleeding stops and you get a BFN in a normal amount of time but it can happen. If you got pregnant before it could potentially cause problems. You can get a scan to check also.
Often doctors recomend it for dating purposes but you can always use OPKs and these days doctors mostly go by dating scans rather than LMP anyway.
There is the general thought that your body and emotions need time to recover. Unless you have a specific problem like an infection, or in my case being anemic, there doesnt seem to be much evidence that you need to wait just to give your body a break. My first period was super heavy so maybe that is a sign things are not back to normal? What is best for you emotionally I think is a personal thing.
Some interesting links on not waiting:
https://www.webmd.com/baby/news/20100805/study-no-need-delay-pregnancy-after-miscarriage
https://miscarriage.about.com/od/tr...before-getting-pregnant-after-miscarriage.htm
https://www.dailymail.co.uk/health/article-1300741/Dont-delay-try-miscarriage-women-warned.html