I've also seen that happen, But I think the reason is the recent "Defi hype" that quite steals the focus on the IEO spotlight, Because base on my observation, not just Binance has experienced it but also in some other top tier crypto exchanges.
And now that the Defi crazed was already fading let us compare the next IEO results in Binance or in other Top exchange that also doing and IEO.
The DeFi trend is indeed a something, if you look at projects like Maker, Curve or Sushi, they can attract traders' attention more easily, in fact almost like in ICO 2017 where everyone dared to spend a lot of money to invest. ofcourse this has an effect on the running of the IEO. but so far the IEOs on Binance are still strong and still able to make the market