A lay often attach 5 strings more than a monk, so buddha has to teach them dāna and sīla, before bhāvanā

Samatha = citta-samatha = Leading to wholesome mind = seclusion of unwholesome in 5 strings, kāmaguṇa.

Vipassanā = samatha-vipassanā = Leading to sabbasaṅkhāra-samatha, nibbāna = seclusion of whole 5 clinging-aggregates.

So, samatha is for taṇhā-carita (unwholesome often arise), vipassanā is for diṭṭhi-carita (wholesome often arise).

People, who can't get the seclusion of unwholesome in 5 strings, should meditate samatha.

People who already got the seclusion of unwholesome in 5 strings, should meditate vipassanā.

It is not depend on lay or monk, it's depend on each personal ability like I explain above.

However, most lays can't get the seclusion of unwholesome in 5 strings, even the seclusion of verbal and bodily actions as well, so Buddha often teach dāna & sīla & bhāvanā (samatha&vipassanā) to lay. But there are more monks who have gotten the seclusion of unwholesome in 5 strings, so the buddha often teach sīla&samatha&vipassanā to monk.

See: Netti-pakaraṇa.