You are competing against much larger rivals. They have huge marketing budgets, thousands of sales reps and partners, brand recognition. It is a tough challenge to sell against them.
There are 2 forms of risk that the customer perceives. Risk # 1 is to change the status quo. Risk # 2 is to go with a relatively unknown vendor or smaller player compared to one of the big giant well known vendors.
Status quo is like a warm blanket on a cold day. It feels safe. Change is risky. Change is scary.
Overcoming these challenges is hard so your sales funnel is unpredictable and you can not repeat enough of your wins in new accounts.