Asset location (Private wealth management)

“ an overly low capital gains tax rate or an overly high marginal income tax rate at retirement would favor equities inclusion in taxable accounts. A low marginal income tax rate would generally favor equities inclusion in tax-deferred accounts “

Could someone explain why should overly low capital gain and overly high marginal income tax rate be in taxable account ?? And vice versa, why should low marginal income tax rate be in tax-deferred accounts ?