The best reason to rollover your 401k to an IRA in a brokerage account is for more choices. Most 401k/ 403b have limited investment options in the form of selected mutual funds. With an IRA, you have thousands of choices in the form of ETFs (exchange traded funds). You can invest in various sectors including communication, consumer discretionary, consumer staples, energy, financials, health care, industrials, information technology, materials, and real estate. The newest ETFs includes autonomous technology & robotics (ARKQ) and Self-Driving EV (IDRV). You can also invest in individual stocks. Your choices are limitless.
In contrast, you may not want that many choices and prefer to have a dozen basic funds to choose from. In this case, you have nothing to lose by keeping your money in a 401k.