What I've observed is that in the early years almost every lender filed a UCC to signal to other lenders that they had an advance out to a borrower, and when a lender received an application that showed a UCC filing they would request a payoff. This was essentially a voluntary and good faith effort and most of the early players cooperated. There were of course the usual retention tactics when calling in for the payoff (transferring to sales, delaying remittance of the payoff, etc.), but by and large if the borrower was forceful enough about wanting to go elsewhere the lender would produce a payoff. Then some of the larger lenders started using aliases to mask their real identity for one (or all) of three reasons: to make it harder to know who to request a payoff from thus preserving the deal on their books, to prevent other lenders from drafting on their underwriting, and to prevent their borrowers getting called by other funders who are calling UCC lists. In response to those phenomenon, lenders responded with more complex UCC masking and fewer UCCs filings altogether. This makes it increasingly difficult for lenders to identify MCAs using the UCC filings.

The bank statements are still a tool that can be reviewed for activity in an attempt to spot MCAs, but if they are on a split or lockbox and the lender doesn't have the processing data, this gets harder to spot again. Further, if the lender doesn't have access to the processing data AND doesn't have the banks that reflect the funding deposit, it gets harder still. Also, merchants share some blame as well. I've seen many merchants run multiple accounts and only furnish the banks for the one that doesn't show the MCA activity. Separate processing and cash accounts, or some even setup accounts that just have the MCA activity flowing through them and/or do bank account changes after funding.

Between lenders trying to preserve their portfolios and retain customers, merchants trying to get as much capital as possible, and scammy funders willing to stack and draft on the initial UW, there are multiple reasons why lenders are missing UCCs. It all boils down to a lack of trust and ethics though, and almost everyone is to blame.