Plaid was originally a budgeting app. After realizing how terrible banking APIs are, they pivoted to building a developer-friendly banking API. Now their valuation is 10B+.
Plaid then got a 2021 round of $425MM at a $13.4B valuation “according to a person familiar with the matter”. https://www.cnbc.com/2021/04/07/plaid-hits-13point4-billion-...
Small businesses are well catered for with tools like Xero, QuickBooks etc.
There's a psychological issue of people treating their budgeting app as the bearer of bad news (shooting the messenger effect), which results in churn.
There's also a high correlation between people looking for budgeting solutions being in a bad financial standing which makes the justification of paying for the software less likely.