Word for the act of accepting something only because it is the unquestioned, traditional standard

I may be wrong but I believe in this context the word to use would simply be "Tradition".

"Samuel never felt distinctly masculine throughout his upbringing, but since his town was very conservative to traditional gender roles, he took on a more masculine appearance throughout his life, and without thought to question, accepted tradition"

Status quo would work here:

Samuel never felt distinctly masculine throughout his upbringing, but since his town was very conservative to traditional gender roles, he took on a more masculine appearance throughout his life, and without thought to question, accepted the status quo.

status quo
(usually the status quo)
    The existing state of affairs, especially regarding social or political issues.
    ‘they have a vested interest in maintaining the status quo’
_{Source: Lexico: status quo}

Update

Since your fill-in-the-blank has been edited from he accepted ______ to he ______, it seems you are looking for a "package deal"—an intransitive verb that means "accept something for the sake of convention" rather the verb accept + a direct object that signifies that convention. So:

Conformed would work here:

Samuel never felt distinctly masculine throughout his upbringing, but since his town was very conservative to traditional gender roles, he took on a more masculine appearance throughout his life, and without thought to question, he conformed.

conform
1 Comply with rules, standards, or laws.
‘the kitchen does not conform to hygiene regulations’
    1.1 (of a person) behave according to socially acceptable conventions or standards.
‘the pressure to conform’
    1.2 Be similar in form or type; agree.
‘the countryside should conform to a certain idea of the picturesque’
_{Source: Lexico: conform}

Merriam-Webster notes:

Conform, with its prefix con-, "with" or "together", means basically "to adopt the form of those around you". Thus, employee behavior must usually conform with basic company policies. A certain philosophy may be said to conform with American values (even if we sometimes have a hard time agreeing on exactly what those are). And a Maine Coon cat or a Dandie Dinmont terrier must conform to its breed requirements in order to be registered for breeding purposes. Being a conformist is usually a safe bet; being a nonconformist, who ignores society's standards and the whole idea of conformity, can be a bit dangerous but also sometimes more fun.
_{Source: Merriam-Webster: conform}

In that passage, you can also find noun forms to work with (was a conformist, showed conformity).

Here's the whole thing again, cleaned up a little:

Samuel never felt distinctly masculine during his upbringing, but since his conservative town expected traditional gender roles, he took on a masculine appearance throughout his life, and without questioning, he conformed [to its expectations].

How about you use the Latin phrase nolens volens?

Here is M-W defining the phrase—

unwilling (or) willing : like it or not

So you could say—

"Samuel never felt distinctly masculine throughout his upbringing, but since his town was very conservative toward traditional gender roles, he took on a more masculine appearance throughout his life, and without thought to question, accepted it nolens volens.

Caving to Received Wisdom.

Cambridge offers the following example:

... to question the received wisdom of more conventional research.

In religion, received wisdom is its orthodoxy.

When a society takes an established convention as its traditional standard, it reverse-engineers the norm as wisdom, the only norm—unquestioned, as handed down from the gods, and thus immutable. Exceptions cause shock.

One person's received wisdom is another's received prejudice.

From Cambridge English Corpus:

We should always be sceptical of received wisdom, or in its rather more dangerous guise common sense, which is often little more than 'naturalised' ideology.

The noun compliance has, as one of its (common) senses, 'meekly accept the status quo':

compliance [noun] [non-count] [formal]

...

(2) [mainly disapproving]

the state of being too willing to do what other people want you to do:

• It's his compliance that amazes me.

[Cambridge Dictionary] (reformatted)

The verb is 'comply', and the idiom toe the line has much the same meaning (probably emphasising the regulatory pressure involved more):

accept the authority, principles, or policies of a particular group, especially under pressure [Lexico]

Follow the crowd overlaps in meaning too, though usually there's less of a sense of dire consequences for non-compliance here.