Trailer fees are paid by fund managers to distributors (i.e. your broker/financial advisor). The distribution commission is paid continuously as long as an investor holds the funds and usually ranges between 0.5% - 1% per annum, or greater than 50% of the fund-level fees. This potentially leads to misalignment of incentives between an investor and distributor, and higher fund-level fees.
Endowus does not accept trailer fees as we want to stay independent and completely focused on building the best portfolios for you rather than selling you products that pay us the highest fees.